sub 30 strokes for 50m is way way way too low! 45 is fine. Where did you read 30 strokes for 50m?
When I swim comfortablly fast I swim 43 strokes for 50m. To compare when I swim the same pace in a 25 yd pool, I swim 18 SPL. My lowest non-drilling in a 50m pool is 37 and my lowest in a 25 yd pool is 14.
So you can use those nubmers to compare...mine are very low for my height, 5'3".
Don't get hung up right now on the number of strokes, because you are probably right in teh range you need to be.
Video would be great. We have a German coach currently living in London, Tracey Baumann of Swim Solutions. She travels to Germany to visit occasionally perhaps you can arrange a lesson!