Google translate:

Hello,

I accidentally deleted a bike from the equipment section. Is there a way to recover the data? Thank you.

Hi ​@Marco.sego,

unfortunately there's no easy way to do this. I’ve seen a similar thread, the user ended up re-adding the accidentally deleted equipment and then correcting all impacted activities manually. 

You can also try contacting Strava Support but it will likely be much faster to fix the activities manually. Anyway, here's how to reach Support: https://support.strava.com/hc/en-us/articles/216917777-How-Do-I-Contact-Strava-Support

Also, there's a feature request open for voting to change the UI - which would hopefully help to prevent situations like this: