“I can't believe you watch this stuff. It's so cheesy!”

Your sister is watching a TV show that you think is silly. You want to tease her for watching it. You say:

I can't believe you watch this stuff. It's so cheesy!

I can't believe (clause)

You say "I can't believe ___" when a fact is surprising or you want to show that you feel strongly about it. You can say this for positive things:

I can't believe we won!

or you can use it for negative things:

I can't believe you left without telling me.

this stuff

"This stuff" means "things like this".

(something) is cheesy

When you say that something is "cheesy", it means that it's not good because it's too cliché or too over-dramatic. You use "cheesy" to describe movies, TV shows, music, books, etc.

Examples of things that can be called "cheesy" are:

• love songs
• soap operas
• cheap science fiction movies
• romance novels,
• bad jokes

...and so on.