A bigger SD card won't make your Internet faster. If it's used on WiFi, it could be faster depending on your ISP (Internet service provider). If it's not on wifi, you're limited to whatever speed your cell service provider determines.
My hardware version is S720C.01 and the firmware version is 2.3.6. SD total space is 1.85 GB, available space is 1.69 GB. System storage available space is 742 MB. My problem is if I get near 100 photos, the photo gallery locks up and I have to remove battery and reinstall to get gallery back. I have deleted photos to 80. So, will a larger SD card fix this?
Unless your phone allows you to move the Gallery off to the SD card, no SD card will help you. That's a cheap phone and it will be slow and limited, intentionally. Go to the phone store and ask them for help with it, if the manual doesn't explain enough about the phone.