I only recently started ( and had to take a little break recently) and am also a teacher, in England. I weigh in at about 154 lbs and 6' so very similar build. I also did triathlons!
Good luck and we'll keep in touch with our progress? Nice to have a German here - your English is better than you think! You put us Brits (and mayber Americans?) to shame with your country's language skils!