I'm gonna try to explain this as good as I can in English.
Yesterday my boyfriend was supposed to install a led ramp at the back of the car (reverse light), it didn't work. When he started the car again and put in reverse the lights where dark, didn't matter what he did. He tried to look at the fuses but nothing seems to be wrong there. When we drove away we realised that the speedometer wasn't moving at all. What do we do? He's handy with cars, I'm not, but he's lost here.
1. What could be the problem?
2. Is there a connection between these two issues?
3. What the h*ll are we suppose to do?
The battery was never out of power and the never pulled out any plugs, he only took out the reverse lightbulb on the right side of the car.
Hopefully someone has an answer.
Thank you!

 

Before we can offer any kind of solution it is important to know EXACTLY what lamp was removed and what # lamp was installed. They are all different and , let's start there, OK ?

 

Ah, sorry.. He removed the lightbulb only at the right side of the car, he did it to try to connect the led ramp to the reverse light. When the led ramp didn't work he put the bulb back at the same socket he took it from. The mystery is that now neither of the lights works when you put in reverse, and the speedometer stays at 0 no matter the speed.
Since I don't know anything about cars and don't know the correct terms in English, I really hope that you understand my explanation! We couldn't find any answers in any Swedish forum, that's why I'm trying my luck here

 

Whatever the case , welcome !
Strange things happen and sometimes to protect the systems a wrong move can cause a fuse to open.
What year and model is your vehicle?