diff --git a/private/Backup.py b/private/Backup.py
index e71599e..35f9bd6 100644
--- a/private/Backup.py
+++ b/private/Backup.py
@@ -4,6 +4,8 @@ import ListUsers
 import csv
 import io
 import lib.CFG as CFG
+import lib.validator
+import lib.UserExceptions
 import os
 
 
@@ -52,6 +54,7 @@ class Backup:
             return None  # @TODO maybe some better output here
         if userids:
             pass  # empty tuple means everything
+        # noinspection PyBroadException
         try:
             with open(fname, 'r', newline='') as f:
                 import lib.sqlitedb
@@ -60,25 +63,45 @@ class Backup:
                 sql = lib.sqlitedb.SQLitedb(CFG.REG_FILE)
                 reader = csv.DictReader(f)  # @TODO csv.Sniffer to compare? When yes, give force-accept option
                 for row in reader:
+                    # if any of this fails move on to the next user, just print a relatively helpful message lel
+                    if not lib.validator.checkUsernameLength(row["username"]):
+                        print(f"The username {row['username']} is either too long(>16) or short(<3).")
+                        continue
+                    if not lib.validator.checkUsernameCharacters(row["username"]):
+                        print(f"The username contains unsupported characters or starts with a number: "
+                              f"{row['username']}")
+                        continue
+                    if not lib.validator.checkSSHKey(row["pubkey"]):
+                        print(f"Following SSH-Key isn't valid: {row['pubkey']}")
+                        continue
+                    if lib.validator.checkUserExists(row["username"]):
+                        print(f"The user '{row['username']}' already exists.")
+                        continue
+                    if not lib.validator.checkEmail(row["email"]):
+                        print(f"The E-Mail address {row['email']} is not valid.")
+                        continue
                     if row["status"] == "1":
-                        sysctl.register(row["username"])
-                        sysctl.lock_user_pw(row["username"])
-                        sysctl.add_to_usergroup(row["username"])
-                        sysctl.make_ssh_usable(row["username"], row["pubkey"])
-                        print(row['id'], row['username'], row['email'], row['name'], row['pubkey'], row['timestamp'],
-                              row['status'] + "====> Registered.")
+                        try:
+                            sysctl.register(row["username"])  # @TODO exception lib.UserExceptions.UserExistsAlready
+                            sysctl.lock_user_pw(row["username"])  # @TODO exception lib.UserExceptions.UnknownReturnCode
+                            sysctl.add_to_usergroup(row["username"])  # @TODO exception lib.UnknownReturnCode
+                            sysctl.make_ssh_usable(row["username"], row["pubkey"])  # @TODO exception
+                            print(row['username'], "====> Registered.")
+                        except Exception as e:
+                            print(e)
+                            continue
                     elif row["status"] == "0":
-                        print(row['id'], row['username'], row['email'], row['name'], row['pubkey'], row['timestamp'],
-                              row['status'] + "not approved, therefore not registered.")
-                    else:
-                        print(f"Uhm, ok. Type is {type(row['status'])}, and value is {row['status']}")
-                    sql.safequery("INSERT INTO `applications` (username, name, timestamp, email, pubkey, status) "
-                                  "VALUES (?,?,?,?,?,?)",
-                                  tuple([row["username"], row["name"], row["timestamp"],
-                                         row["email"], row["pubkey"], row["status"]]))  # @TODO: without IDs
-                    pass  # @TODO: Import with sqlitedb and system. Will be fun Kappa
-        except OSError as E:
-            print(f"UUFFF, something went WRONG with the file {fname}: {E}")
+                        print(row['username'] + "not approved, therefore not registered.")
+                    try:
+                        sql.safequery(
+                            "INSERT INTO `applications` (username, name, timestamp, email, pubkey, status) "
+                            "VALUES (?,?,?,?,?,?)", tuple([row["username"], row["name"], row["timestamp"],
+                                                           row["email"], row["pubkey"], row["status"]]))
+                    except OSError as E:
+                        pass
+                        print(f"UUFFF, something went WRONG with the file {fname}: {E}")
+        except Exception as e:
+            print(f"Exception! UNCATCHED! {type(e)}")
         return True
 
 
diff --git a/private/lib/UserExceptions.py b/private/lib/UserExceptions.py
index 02e8f47..926c8e5 100644
--- a/private/lib/UserExceptions.py
+++ b/private/lib/UserExceptions.py
@@ -18,5 +18,30 @@ class ModifyFilesystem(General):
     pass
 
 
-class HomeDirExistsAlready(ModifyFilesystem):
+class SSHDirUncreatable(ModifyFilesystem):
     pass
+
+
+class SQLiteDatabaseDoesntExistYet(General):
+    pass
+
+
+class User(Exception):
+    pass
+
+
+class UsernameLength(User):
+    pass
+
+
+class UsernameTooShort(User):
+    pass
+
+
+class UsernameTooLong(User):
+    pass
+
+
+class UsernameInvalidCharacters(User):
+    pass
+
diff --git a/private/lib/validator.py b/private/lib/validator.py
new file mode 100644
index 0000000..82283d0
--- /dev/null
+++ b/private/lib/validator.py
@@ -0,0 +1,52 @@
+import re
+import pwd
+
+
+def checkUsernameCharacters(username: str):
+    if re.match("[a-z]+[a-z0-9]", username):
+        return True
+    else:
+        return False
+
+
+def checkUsernameLength(username: str):
+    if len(username) > 16:
+        return False
+    if len(username) < 3:
+        return False
+    return True
+
+
+def checkUserExists(username: str):
+    try:
+        pwd.getpwnam(username)
+    except KeyError:
+        return True  # User already exists
+    else:
+        return False  # User doesnt exist
+
+
+def checkSSHKey(key: str):
+    # taken from https://github.com/hashbang/provisor/blob/master/provisor/utils.py, all belongs to them! ;)
+    import base64
+    if len(key) > 8192 or len(key) < 80:
+        return False
+
+    key = key.replace("\"", "").replace("'", "").replace("\\\"", "")
+    key = key.split(' ')
+    types = ['ecdsa-sha2-nistp256', 'ecdsa-sha2-nistp384',
+             'ecdsa-sha2-nistp521', 'ssh-rsa', 'ssh-dss', 'ssh-ed25519']
+    if key[0] not in types:
+        return False
+    try:
+        base64.decodebytes(bytes(key[1], "utf-8"))
+    except TypeError:
+        return False
+    return True
+
+
+def checkEmail(mail: str):
+    if not re.match("(^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$)", mail):
+        return False
+    else:
+        return True