Three things I suggest before you start throwing money at this.
Do you have and have you ever used a multimeter to check continuity? If you do not I would say start by getting one of them as it will pay you back 10 fold when working on multirotor craft. Just a cheapie 10 or so dollar one from walmart or amazon will be good enough
Two practice soldering on junk electronics. Those solder joints look pretty heavy handed and could potentially be where things are going south for you. This is where a decent temp controlled soldering station really pays off. Specially if you have a pointy tip for the smaller stuff we mostly work on as well as a chisel tip for things like power leads or XT60 connectors. Look for one in mid level price ranges thats states it is a fast recovery iron. the older irons leach heat fast and take for ever to catch up with a larger joint thus super heating the board and surrounding sensitive components.
Third is what we call a smoke stopper. Which is nothing more then a car tail light bulb you put in line between the battery and the electronics whenever first powering up a new build so you dont fry components.
These may help more then explaining it all in text.