Video Editing low FPS

Hi folks!

Videos runs at 29.97FPS

I decided to create something better for my upcoming YouTube covers, but now I have a lot of layers. (Fade in, Fade out, my logo, a banner with the title of the song, etc.) and when I play the animation it runs really slowly (4FPS).
It won’t be possible for me to synchronize the sound and the video anymore without a higher FPS.

How can I have more FPS ?

Here’s how it looks

I highlight the audio and video, those are the strips that needs to be synchronized.

I even deleted the other layers but it does nothing to the FPS.
I tried AV Sync (which normally synchronize the audio and video), Frame drop and no sync but nothing works.