Help / Advice needed

Hi guys.
In the last week I have returned to swimming after many many years away from it.
I am from the UK, 57 years old, weight is around (18st / 252lbs, heavy built) and would like some advice on how to be more efficient in the water.

I read the book many years ago and it really taught me alot, especially about the glide section of my style.
I have a Garmin swim and today I was doing 25m in 31-32 seconds, 50m in 103 - 110sec and 100m in 2min :19sec - 2min:30 sec, I don't do a proper turn. My stroke count is between 13 to 14
I do struggle with floating and have been told my legs drag below me.
I am a black man and there is a romour that we do not make good swimmers.
Any advice would be appreciated

Regards
Keith