I changed my battery!
So this is how it went...
1) 30 minutes trying to unscrew the back open with a screwdriver that is too small...
2) 3 screws came off but somehow mess up the 4th screw... and now whatever I do, it just wont come off...
3) After countless tries, the screw wouldn't come off and so I just force the back open with my bare hand... doing so, I broke the last screw.
4) luckily when the screw flew out, everything inside is still intact.
5) now it's time for the battery latch! which took 20 minutes
6) I couldn't find the right tool... and decided that I don't need any tool for it afterall, again I forced it open with my bare hand (fingernail) :-D
7) After I put in the battery... the watch had no display! OMG! took me another 5 minutes to find the AC reset, and I simply used a needle and poked at it...hoping for the best.
8) now everything is back in order, but the button wouldnt work. I guess because they were misaligned. Anyways, I don't know what I did to fix this problem, but I pressed my buttons for about 40 times and that somehow aligned the button with the movement again. I tested out the lamp and the alarm and everything is ALRIGHT!
9) I just want to say I love this whole experience and overall it wasn't so hard. But I don't think my watch is waterproof anymore because I lost one screw, hopefully in the future, I'll drop by a shop and find the right screw for it
maybe next time I change a battery on my watch, it'll at most takes 10 minutes