iPhone 5, won't start after repairs(battery+dock connector)

Hi,

I'm have no clue how to solve my problem so I hope you can help me out.

Problem:

The iPhone 5 was taken into repairs by a shop but they didn't do a good job and the phone was given back.

problem that occured was that the charging would only be on 1 side of the cable and that the phone didn't charge properly after a while.

Note: when I opened the case I saw they removed these plates.

1. https://d3nevzfk7ii3be.cloudfront.net/ig...

2. https://d3nevzfk7ii3be.cloudfront.net/ig...

I repaired the lightning dock connector + battery as they both weren't working, but after putting everything in place It simply did not work.

Steps I tried:

1. LCD from other iPhone

2. Battery from other iPhone (brand new phone)

3. Charge battery in a new phone(worked)

4. Charge battery in new phone and then place in old phone (now this was my final step and attempt since if this worked, it must've been the connector.)

Stuck:

After doing step 4 from above, I started the iPhone and in a matter of only 1 minute the phone started to heat up + no screen or working phone, I quickly disconnected the battery after 1 minute. So I'm stuck right now and clueless what my best bet would be to determine what's wrong with the phone.

Every piece of help is appreciated and the helping feedback is more then welcome!