Samsung galaxy s5 water damage

[Rvdb]

Hi all,
First of all, Don't mind my english i'm Dutch so it is not great.

So my Samsung suffered from water damage, at the pool the bag it was in got wet and so did the phone.
There are 2 symptoms right now, the phone reboots itself whenever I lay it down on the table. If I keep it in my hand it doesn't reboot. Secondly it doesn't read my sim-card anymore.
For my insurance I had to send it to a repair company to get it repaired, but they told me the repair costs where higher then the value of the phone so they did not repair it.
Now my question is: do you think that it is worth trying to repair it myself? Everything works perfectly except the 2 problems I mentioned above. And if it is worth trying what do you think needs to be replaced? I was thinking the sim card reader for starters but I have no idea what causes it to reboot itself so often.

I would really appreciate your help, thanks in advance.