Is it normal my microwave interrupts my wifi?

It's not an unknown phenomenon, since the frequency of the electromagnetic waves produced by a microwave to cook food is very close of the frequency of the electromagnetic waves used for WiFi.

If turning on a microwave oven causes your WiFi to drop, that means the signals transmitted and received by the router are being swamped by a much stronger signal from the oven. So your oven is clearly leaking microwaves. That should never happen with a well-made and undamaged microwave oven, since the microwaves should never escape the metal box of the oven or get past the metal screen behind the glass door.

If I were you, I'd replace the microwave as soon as possible. If that's impossible at the moment for some reason and you have to use it, I'd make a point of keeping a good distance from it when it's on. WiFi signals are very weak and easily overpowered, so it's probably highly unlikely that you'll end up having your innards cooked by the stray microwaves if you stand close to it when it's on, but there's a good reason why microwave oven manufacturers always include a switch that switches it off when you open the door, rather than saving some money by not including that feature.

If your WiFi router and the equipment connected to it includes an option of using the 5GHz band, you could try switching to that since it's out of the frequency range of the microwave oven. Still, you really should look at replacing the oven.

If your microwave is leaking that can cause all sorts of problems, it's a health risk too. Used to to work on guidance systems, communications, and radar, real care was taken when testing the microwave gear!

I remember when my old microwave violently shook when it was cooking stuff. I would wonder when it would finally explode and what would take it to explode. Perhaps a Turkey would get it to finally die. Moved out before I got an answer.

Whenever anyone takes a shower in our hall bathroom, the internet in my bedroom slows down. There's a simple explanation for it. The microwaves generated by your microwave are interfering with the light created by your wifi router. Essentially, the light made by your microwave hits the light made by your wifi router, changes the direction it's moving and the speed at which it moves, making the wifi of poor quality. Of course, this only would prove to be the case if your microwave is between your device and the wifi router; if not, I have no clue what the answer is. If that is the problem, move the microwave, your device, or the wifi router, so that the microwave isn't in between the two.