Preview in After effects not working anymore

Hello,

First off all some information:

I used After Effects 2019, then this problem came up and i switched to 2018 (problem is still there).

My laptop is a Lenovo ideapad 500.15ISK with an Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz 2.60 GHz processor and with 12gb installed RAM.

so basically my problem is the following:

Whenever i try to preview my project, the frame rate goes down to around 20fps (from 30/29.97).

Even if there's nothing in the comp it won't preview properly.

I've set down the resolution to quarter and still: same problem.

I've tried everything possible, even resetting my laptop (2 times!!) but still, the problem came back.

But a few weird things i noticed in ae were, that whenever i try to preview, this little "play" button turns into a square instead of this II> symbol.

And when i turn off this eye (look at the photo please) it works properly again.

Can anyone please help me?