Leonhard Bokowski

Try another game if that works to see if it's the game or the 2ds that's broken. Replace the broken one by either getting it fixed by Nintendo or ask the place you bought it from.

It might be a broken Wifi chip, which isn't replacable. Try powering it on and instantly disable wireless communication. If that works try reattaching the antenna and then enable wireless again.

Your Bluray drive is failing. You can try cleaning the laser but you might need to replace other components depending on the issue (disc not pulling in=one of the motors, disc not spinning=drive motor, disc spins but can't be read=problems with the laser)

Put everything back onto the sd, the 3ds won't work without it! If that doesn't work, get a flashcart (such as the r4i) and follow the steps on https://3ds.guide/ntrboot to reinstall CFW and get everything back to normal. Let me know if you need more help, I've done it about 5 times and know how it works.

Did something happen? Did you drop it, spill something on it or did it randomly stop working? It's usually a ribbon cable that got loose or if the hinge is broken then the ribbon is most likely ripped

Aliexpress. Also the sliders are all the same. Get any slider and it will work

Does it show red lights? If so, that means your Xbox is broken. Search for Xbox rrod and there will be a lot of pages that explain the issue. You can usually get it fixed for about 40$

Could be that there is dirt inside the buttons (the actual buttons that control the circuit, not the plastic outer ones) or that they are bent in some way. Try to get Nintendo to fix it because there are almost no spare parts available yet.

Nothing. Get a new one. It seriously costs under 2$

Check your ping. You can have all the speed you want and still have it lag because of a bad ping (0-20 is good -50 is ok and anything above that is bad)