Hi @maxmax0202xamxamo, welcome to Thunkable! 
Be sure to check out our posts about How to ask Great Questions v2.0 and our Community Guidelines as you get started.
There are quite a few other topics already discussed about this, you can see the search results for that here. The general idea will be that you’ll want to created a stored variable for each language and the user can select their preferred language. Once that is done, you can use the blocks and logic to update labels, button text, etc. to run the copy in the preferred language the user has set.