A1 and B17 together?

Hello, I’m almost 17 and I’m almost finished with my B17 (theory finished, compulsory hours completed, only practical exam ). All good and nice, but it actually brings me quite little in terms of mobility. Up to now I have driven with the 25 kmh mofa, which has not been enough for me for a long time, and have long been interested in something stronger. Now I wonder if it is still worth doing the A1, since I could already do the A2 at 18. I will be able to do the A2 after the Abitur v Is this why you think I should do the A1 anyway? Can I save money if I do it together with the current training?And my last question: My father always tells me at 18 or 19 that he is not enough for a 125cc anyway. What do you think about it? Thank you very much in advance.