I have a 6'10 NSP Mini-Mal and I've been surfing for about 3 months. I can get up on every wave I take, I can turn a bit and I can take most waves other surfers with shorter boards and bigger arm muscles can take

I have a problem though, most of the time I will end up taking a wave on the non-broken/foam part, ride it a bit, then the foam will catch up with me and I won't be able to generate enough speed to stay ahead of the wave. I end up falling in the foam mid-wave and mid-impact zone which is a pain at times if there's a series coming (including the 1-2 surfers that have to avoid me until I swim out of the impact zone...)
I currently have a tri-fin setup but I was wondering if a dual fin or even single fin setup would help me be able to turn better/keep ahead of the foam and generate more speed...
I don't really want to resell this board and buy a shorter one just yet, mainly because I am moving away from surf in about 5 months and I won't be surfing very often after that.
Could it also be the way I'm riding/positioning myself on the board that cause me to loose speed early on in my ride?
All tips are appreciated
