Reset keyboard (at symbol)

Hey,

My Macbook started doing weird stuff with the keyboard and I couldn't use shortcuts like cmd+space for Spotlight etc. I found the keyboard settings and was able to reset those but my problem now is that I can't type the at symbol anymore for some reason. I have a german keyboard and usually it is alt+L. All the other commands work for that (eg. alt+E for €). If found the key comibnation for the at symbol but it is annoying and I want it back to how it was! Could someone help me? Right now it is option+alt+L.

Just to clarify: Changes had nothing to do with any updates or what so ever.

Cheers

Constantin