In my world survival my fps is low, (okay I've done a lot in it), but in the oceans generated in the aquatic update fps also falls, and in the mansion this also occurs. My Device is a Samsung Galaxy S4 Mini (GT-I9192).
MCPE-35758
Low fps
Resolved
Invalid
0
(Unassigned)
Unconfirmed
Phone - Android - Samsung Other (Specify in description)
4.4.4.
1.5.0.14
Retrieved
I'm sorry to say this, but the Samsung Galaxy S4 Mini simply isn't one of the newest phones anymore. According to Kimovil.com it has a total Antutu Benchmark score of 14.659, which is very-VERY low.
So, the reason why you're having a low framerate and why your friends are able to start Minecraft quicker than you is actually that your phone is just really, really slow.