I'm sure your intentions were good. You just started on a wrong foot: you usually don't start by asking favours, claiming that you can not do anything.
You also don't start a topic, claiming you want to buy repro carts (most of us dislike those), or that you want something done and give money in return.
Third thing: you need to know the english language to communicate. Guess what, it is not my first language either, but hoping for a guide, or an utility in your language is highly unlikely. I knew someone who wanted to know a solution to some problem, but he could not write one understandable sentence in english (so no help could be made).
Fourth: wanting to hack games like Final Fantasy or Zelda3 A link to the Past on GBA sounds kind of strange as well. Final Fantasy's main consoles were NES, SNES, and later parts on Play Station. GBA versions are a poor re-releases, for which you can not hope for a solid editor for various reasons.
By the way, hex is math. It is actually quite easy to understand. 10 in hex is not 10 in dec, but rather 16, which is 2x2x2x2. So the hex numbers start at 00, go to 09, then switch to the 0A to 0F, before switching to 10.
That's why one 1MB is not 1,000,000 bytes, but rather from 00000-FFFFF, making it a 100000 long in hex, which is 1,048,576 in dec. Binary is just 1 and 0. Dec: 1, 2, 3, 4; binary: 1, 10, 11, 100. Example: 11 in dec is 0B in hex is 1011 in bin.
You might want to start here and learn this "new computer-math". You just need a windows calculator. And also the address-pointer calculator for calculating pointers.
I recommend to you to stay away from GBA and rather try to work with much more easier NES and SNES engines. You can expect much better utilities and hacks for those versions. You need a lot more skill for GBA or DS.