Hate to be the one to break it to you, but that board needs some professional help.

Someone has replaced the old, leaky battery but neglected to clean the damage.
This means the corrosion has not been properly arrested. 

Also, Welcome to the forum.

Yep It needs all that corrosion removed and nearly all the components in that photo need to be replaced ( there is corrosion on nearly every leg)
the solder through pads need to have the solder removed  and the corrosion neutralised also.