Well, yesterday I had the second appointment in the hospital to check the current shape of my ankle. As I had expected, I could hand back the crutches I got for the past week. Instead of this I got a stiff fixture on my ankle which allows me to move almost normal again but prevents tilting my foot and causing additional ruptures to my damaged tendon.
Of course I've got the expected additional constraints. I have to wear this fixture for six weeks and after that I should stay away some time from indoor sports, which usually are fast sports with high forces on the feet. Instead I should train the muscles to support my foot stability and lower the risk of future weaknesses.
But I was also told that after some additional resting time from now I can also start with easy sports, like running, to shorten the recovery time a bit. Or at least to make the reentry into sports not that sudden with the end of my ankle-stabilisation phase.