diff --git a/pybackup.py b/pybackup.py
index f8d73df..bcc3d70 100644
--- a/pybackup.py
+++ b/pybackup.py
@@ -1,10 +1,14 @@
 #!/usr/bin/python3
 
 import sys
+import os
 import json
+import subprocess
+from datetime import datetime
 
 # CONFIGURATION_PATH = "/etc/pybackup.conf"  # for "production"
 CONFIGURATION_PATH = "pybackup.conf"  # for testing
+BACKUP_NAME_PATTERN = "%m%d%Y_%H-%M-%S.pybackup.tar"  # DON'T CHANGE THIS IF YOU DON'T KNOW WHAT YOU ARE DOING!
 
 
 def log(message: str, log_level: int) -> bool:
@@ -19,12 +23,18 @@ def log(message: str, log_level: int) -> bool:
     return True
 
 
+def make_backup(path_from: str, path_to: str):
+    backup_name = datetime.now().strftime(BACKUP_NAME_PATTERN)
+    tar_backup = subprocess.run(["tar", "-cf", f"{os.path.abspath(path_to)}/{backup_name}", path_from])
+    if tar_backup.returncode != 0:
+        log(f"Something went wrong handling the backup of {path_from}", 3)
+
+
 # just to make sure this program isn't used as a module
 if not __name__ == "__main__":
     print(f"[{sys.argv[0]}]: THIS BACKUP PROGRAM IS NOT A PYTHON MODULE!")
     exit(0)
 
-
 conf_f = open(CONFIGURATION_PATH, "r")
 try:  # load the config if possible
     conf = json.load(conf_f)
@@ -44,8 +54,9 @@ for _location in conf["locations"]:
     try:
         _location["name"]
     except KeyError:
-        log(f"The {counter+1}th element of locations in the config has no name. Skipping this backup path...", 3)
+        log(f"The {counter + 1}th element of locations in the config has no name. Skipping this backup path...", 3)
         conf["locations"].pop(counter)
+        continue
 
     try:
         _location["path"]
@@ -53,7 +64,81 @@ for _location in conf["locations"]:
         _location["frequency"]
         _location["versions"]
     except KeyError:
-        log(f"The {counter + 1}th element with the name \"{_location['name']}\" of locations in the config is corrupted. Skipping this backup path...", 3)
+        log(f"The {counter + 1}th element with the name \"{_location['name']}\" of locations in the config is "
+            f"corrupted. Skipping this backup path...", 3)
         conf["locations"].pop(counter)
+        continue
+
+    if type(_location["versions"]) != int:
+        log(f"The value of \"versions\" must be an integer, which isn't given in {_location['name']}. Skipping it.", 3)
+        conf["locations"].pop(counter)
+        continue
+
+    if type(_location["frequency"]) != int:
+        log(f"The value of \"frequency\" must be an integer, which isn't given in {_location['name']}. Skipping it.", 3)
+        conf["locations"].pop(counter)
+        continue
+
+    if not os.path.exists(_location["path"]) or not os.path.exists(_location["backup_path"]):
+        log(f"The {counter + 1}th element with the name \"{_location['name']}\" of locations in the config has a "
+            f"wrong path and/or backup path set. Maybe you spelled it wrong? Skipping this backup...", 3)
+        conf["locations"].pop(counter)
+        continue
+
+    if not os.path.isdir(_location["backup_path"]):
+        log(f"The backup configuration \"{_location['backup_path']}\" has no folder set as a backup path. "
+            f"Skipping it...", 3)
+        conf["locations"].pop(counter)
+        continue
+
+    if not os.access(_location["backup_path"], os.R_OK | os.X_OK | os.W_OK) or not os.access(_location["path"], os.R_OK):
+        log(f"Backup configuration \"{_location['name']}\": no access to the path and/or backup path. "
+            f"Skipping it...", 3)
+        conf["locations"].pop(counter)
+        continue
+
+    if _location["frequency"] == 0:
+        log(f"Frequency can't be zero (0), but it seems {_location['name']} has this frequency! Skipping it...", 3)
+        conf["locations"].pop(counter)
+        continue
+
+    for entry in os.listdir(_location["backup_path"]):
+        try:
+            datetime.strptime(entry, BACKUP_NAME_PATTERN)
+        except ValueError:
+            log(f"The backup folder {_location['backup_path']} contains files different to the backup files which is"
+                f" not supported. Skipping this backup...", 3)
+            conf["locations"].pop(counter)
+            break
 
     counter += 1
+
+
+# the REAL backup procedure now!
+for location in conf["locations"]:
+    path = location["path"]
+    backup_path = location["backup_path"]
+    frequency = location["frequency"]
+    versions = location["versions"]
+
+    # backup if there's no backup yet
+    if (backup_folder := os.listdir(backup_path)) == []:
+        make_backup(path, backup_path)
+    else:
+        # backup if the last backup is 'frequency' days old
+        backup = True
+        now = datetime.now()
+        for entry in backup_folder:
+            timedelta = now - datetime.strptime(entry, BACKUP_NAME_PATTERN)
+            if timedelta.total_seconds() <= 60*60*24*frequency:  # if the backup was made before less than frequency
+                # days
+                backup = False
+                break
+        if backup:
+            make_backup(path, backup_path)
+
+    # last, if there are more than version backups in the folder, remove the oldest
+    if (backup_folder_len := len(os.listdir(backup_path))) > versions:
+        files_to_be_deleted = sorted(backup_folder)[0:backup_folder_len-versions]
+        for file in files_to_be_deleted:
+            os.remove(f"{backup_path}/{file}")