

As my dad passed away i inherited his old bike, a cube ams hpa 100 (i dont know the year, should be around 2014ish).
I rode it from time to time and really loved it but now it seems that the fork has given up:
Last time i rode it, the red cap (including a long silver rod) flew off and the fork sprayed oil everywhere. Since then the rebound is very very slow.
I dont really know what to do now. Id love to repair it but im a total newbie when it comes to stuff like this. I figure that this isnt just a sma repair right?
Replacing the fork would be an option, too (really anything that lets me use the bike again is fine), but it seems kinda hard to find a replacement given that the bikes so old and has 26" wheels.
What would you guys do?
Any help is greatly appreciated!