Sqaure boxes replacing all my texts.

I am a very begineer to ubuntu 18.04 . I recently downloaded 5 fonts from the internet and installed all of them . The system didn't warn me any thing.When I turned on my laptop after few hours and logged into my account all my texts were replaced by square boxes and except google chrome which was not my default browser was replaced by square boxes. Terminal also had square boxes. Mozilla didn't open. Neither was my new app that I installed was opening. Please help me!! I dont have dual OS and the laptop which I bought recently is facing this problem so please help me urgent