Why is my Internet so bad?

I've asked this question before and idk the actual model so here is the a video of the router.https://photos.app.goo.gl/3n57cPtYE5p2AWij7

My problem is that it's just super terrible and has a lot of bad connections, also when I'm upstairs in my room which is right above the router, my phone will have low signal strength and sometimes disconnect from the Internet and says that it sees the internet (att166) but when I press on it to connect it will just say saved. My phone is a Google pixel 6 but I don't think the problem is my phone bc I've upgraded my phone a few times (Moto g power to a Samsung a23 to my Google pixel) thinking it was my phone but the same thing happened on all of them.