Workouts to improve breaststroke sprints

Hey outthere, I'm a 16yrs old youth and I'm currently working on some workouts to help me improving my time on 50m ***. Regardless of some people warning me about it, I am selfcoaching and it seems to work as I cut off my 50 *** time by at least 15 secs. (I started with 1:08s in early Dec and just reached the 52,5secs yesterday) As I usually go to the pool twice a week I would like to create a set of 4 different workouts with different focuses (endurance, sprint, technique e.g.) to avoid a routine and continue on going down the time ladder. I already made up two workouts but also they seem to work as I can complete them fairly well if some on really knows some thing about the subject could have a look over them for me and correct them as nessacary and also help me with the rest of the workouts. Btw I recently read that doing a lot of breaststroke isn't that good for the knees. Is that right? Does it mean that I should do less breaststroke in my workouts? Thanks for ya help Matthias