How can I prevent my next bike from being stolen?
That sucks. I'm sorry that your bike was stolen.

If thieves are willing to break into a locked garage, break into a locked and fully enclosed mesh bike parking area then cut two bike locks using power tools: there's not much you can do about it.

If there are lots of bikes in the bike parking area you can make your bike a lower priority target by increasing the number and strength of the locks, and by making the bike itself look less desirable.

Looking at the first picture, it seems the bike parking area door could be easily opened from the inside. The thieves were able to cut a hole in the door and reach the door release - not the most secure setup. Also, it's likely that someone let them into the garage - i.e. one of your neighbors.

Just store your bike in your apartment if you can.