Whenever i add a mob into the config file i cannot start the game beacuse it crashes.

Woudl you be able to send what's in your config file plus the log?

When does it crash?

This is what i put into the config file (github doesn't support .toml files so i coppied the script):

[general]
	#Entities that follow the player after sneak right-clicked. (uses either classname e.g. ZombieEntity or registry name e.g. minecraft:zombie)
	entityWhitelist = [minecraft:villager,minecraft:iron_golem,minecraft:snow_golem]

crash-2021-08-12_16.33.59-client.txt
latest.log

Here are the files you asked for, i'm not sure why the month is in polish but i don't think it's a problem at all. Also there is a list of all the mods i used in these to files.

The game loading was normal but in the moment the main menu should have opened, i saw this:

And then the game crashed.

I hope I anwsered all you questions.
Also just in case you should know, i am using Tlauncher.

I was moreso looking for the latest.log file in your logs folder as the mod should spit out any errors in there instead of crashing.

The formatting looks a bit weird to me as well, If you can send the logs I'll take a look and see if I can find the issue.

The formatting in your config file is wrong, each entry in the config should be in the string format e.g "minecraft:villager", "VillagerEntity", with the speach marks included.

This is what i put into the config file (github doesn't support .toml files so i coppied the script):

[general]
	#Entities that follow the player after sneak right-clicked. (uses either classname e.g. ZombieEntity or registry name e.g. minecraft:zombie)
	entityWhitelist = [minecraft:villager,minecraft:iron_golem,minecraft:snow_golem]

crash-2021-08-12_16.33.59-client.txt
latest.log

Here are the files you asked for, i'm not sure why the month is in polish but i don't think it's a problem at all. Also there is a list of all the mods i used in these to files.

The game loading was normal but in the moment the main menu should have opened, i saw this:

And then the game crashed.

I hope I anwsered all you questions.
Also just in case you should know, i am using Tlauncher.

Yes it is working, thanks for help.
I would suggest you changing the note in the config file by surrounding ZombieEntity and minecraft:zombie with quotation marks.
It would look like this:

[general]
	#Entities that follow the player after sneak right-clicked. (uses either classname e.g. "ZombieEntity" or registry name e.g. "minecraft:zombie")
	entityWhitelist = []

With this change it will be clearer for the users how they are supposed to do the formatting.