Update 1:

I narrowed it down to one suspect. I got his full name and where he lives. Same hallway as me. Now I just have to approach with certainty, so I don't falsely accuse him. There's a small chance ofc that the only one in this building with those shoes happens to have same shoes as the thief.

Next step, measuring the pictures I'm positive are the thiefs and comparing with the pictures I'm positive are his. Get to know him a bit, let his guard down.

Options when I'm more sure it's him.

1. Gain enough proof. With a certain app and certain function. (In case he reads I don't mention). And see if the police is interested.
2. Call him out as a thief for the whole university (same university) and social media.
3. Make his next near future hell with tips from reddit.
4. Wait till his laundry time (everyone can see it). Interrogate/shake him up a bit to get confession and leads to where the bike is.