If these very small plastic legs get stuck in the switch, grasp a needle far in front with a pair of pliers and insert it into the stuck leg and then pull it up with a jerk. This worked very well for me and several times.

The CTRL key has also broken off. Unfortunately, I can't remove the broken part from the keyboard and so can't buy a replacement key. Does anyone have an idea how I can remove it?

Unfortunately, it probably won't be that easy. Try Amazon or Aliexpress. If you don't find anything suitable anywhere, then either tinker with it yourself or look for second-hand items.