Underground internet connection, what to do?

I really don't know what to do.

We have never had particularly good internet here at home, but always in such a way that you could play online at least once (for example games like Fifa, Rocket League or similar). Often we had the problem that the internet (especially on weekends) just stopped working towards evening. The Wi-Fi was displayed, but a connection was no longer possible, for whatever reason. It usually doesn't work until the next day. In my opinion, this problem was due to the WLAN repeaters, because if you unplugged them, you still got the signal from the main router and you could use it to access the Internet.

My father was totally annoyed by the whole thing and so he tried to fix it with a network cable that was placed in the appropriate room from the main router.

Now to the real problem. Let's leave it out of the fact that it is still smeared on Saturday evening (like yesterday), only since we fiddled with the router my internet connection has been so catastrophically bad that I'm no longer able to play online. My ping at Fifa, which was usually 16-20, is now beyond 50 even with a LAN cable, but when it is 30 it still jerks unbearably. The same applies to Rocket League or other games.

The speed test looks bad, of course, from the playstation with lan cable about 10mb in the download and 800kb in the upload. What just annoys me that it used to work and now, as if by magic, it no longer works.

Does anyone know about it and can recommend something I could do? Or does someone have a guess what the problem could be?

Since we tinkered with the router

I guess you changed something in the configuration of your router. Since I don't know anything else, I would simply recommend you go back to the settings and change the things back, or reset the entire settings

Okay, stupid question but how do you do that? I've never done this before, and I think my dad won't be thrilled when I confront him about wanting to reset the internet

You can still see that the router is not near metallic objects or blocked by a wall. Check the LAN cable to see if it is properly inserted.

If you don't want to reset the settings, you can set the frequency range to 2.4 gHz or 5 gHz (if not already) so that full transmission power is available for one range. You can switch the radio channel from the standard to another so that it does not overlap with those of neighbors.

Many routers have a search function in which you can simply search for them or you go through everything individually and maybe find a few helpful settings. With my router that was one of the very last points