I've already checked on netflix if there's my hero academia but I don't think you know where to watch it
Anime on Demand (chargeable with subscription)
otherwise illegal
On Anime on Demand there's season 1-3 with German dubbing, season 4 with subtitles and the film "My Hero Academia - The Movie: Two Heroes".
AoD is quite expensive, but I don't know if there's so much to stream anywhere else.
Yes, I was on Netflix. But it was taken down.
A free alternative would be ProSieben Maxx, where My Hero Academia is currently running, but only season 3.
Anime on demand
Seasons 1 to 4 of Anime on Demand. 1 to 3 with dub and sub. 4 only sub
Season 3 is currently running on Pro7 Maxx