I want to buy a large memory card which is suitable for my cell phone. Will it speed up my phone?
It depends the speed read/write, bigger speeds always choose. Next your memory card can be not compatible with Nokia 5233
if you read here you find that them also didnt met a great speed in their test
so possible its not an isolated case
you can try this soft Speedy GO!
Benchmark using SPMARK, with memorycard and without to see difference
The only real benefit you will get from a larger memory card is more storage space, because it will not affect the processing speed or the amount of RAM your device has. In fact, it can even make your device a bit slower, especially in terms of start-up times, but only because it needs more time to properly detect all your files. You can test if your device suffers from this (if you happen to have a memory card installed) by turning it off, removing the memory card, and then turning it back on. If you notice it becomes ready to use faster than when the card is installed, then be assured that the larger the card (and the more files you have on it), the longer your device will turn on.