You can save this, I have faith in you. DO NOT LISTEN TO "THE RC GUY"

Dont use a solder gun, your shooting your self in the foot with that thing. Also dont use some wimpy iron like billdelong(lol chisel tip), get a good soldering station like , or get a weller. I'm sure you can find either in Singapore.

Second get some really good solder, something like this . I had some cheap Chinese crap that gave me problems just like your having.

Then get a good solder sucker or desolding wick. Something like
After you get these things, which are quality of life upgrades. Your going to need to add some fresh new solder to those contacts, get some good solder mixed in the bad stuff. This will help the solder flow out. To get the solder out, use your solder sucker, it's better for removing large build up.

Please dont throw this esc away, you can save it.

TXloser, you didn't throw that away did you?