I have a problem with running steam, can you help me?

This image shows the problem, can you tell me what to do??

Are you on Windows 10?

What is your system & Steam language?

What are you trying to do when you get this error?
Install the Steam Game Manager?
Install a particular game? If so, have other games installed without a problem?

I'm on windows 10, before trying some things on my windows for protection, everything on steam worked, but there were many other problems, I can't go back to the old settings because all the good work will be lost... Steam language is English, system language is Bulgarian but before that was not the problem! The error appears when I try to open steam.

Ltp2 said:

system language is Bulgarian

Reason I asked about language is the error message complains about non-ASCII, which suggests language mismatch. I have 2 alternative suggestions:

1. Look at the folder path where you have Steam installed, I bet there's a Cyrillic character somewhere. Change that so all the path is ASCII characters.

2. Change the Steam language to Bulgarian. Click here for Instructions.

before that was not the problem

Sure, but you've made many changes since. Those, plus ongoing Steam and Windows updates, mean your environment is different now. C'est la vie :)