Troubleshooting Broken Headphone Jack on Huawei P9 Lite: One-sided Audio Issue

Yesterday, wanting to listen to music, I encountered a problem, namely after connecting the headphones and selecting a song, this problem appeared one of the headphones did not work, at first I thought that the problem lies with the headphones because I have them for some time and you know they could go wrong, but after you arrive home I took new headphones and connected thinking that the problem lies with the headphones I tried with five other headsets and the same each time. This morning I saw something interesting, pushing the plug from the side, the headphones began to work normally and when I let go they stopped. What could happen? I am asking for a quick answer, maybe someone has already met it.
If it is important, the right handset has not always worked.

There are two options. Either the HF socket is dirty or the socket has already received moisture. There are two solutions, either you add a phone to the service, or you can cut it out and clean it yourself.

I don't know if it is dirty ... how to check it and how to clean it ??? The second option is more likely it rains a lot lately and the phone itself was not flooded but the humidity was quite large and I walked with it in a soaked jacket ... what to do to fix it (I would prefer not to return the phone to the service because once on the phone I have a lot of private and needed things and two I travel 16km every day and somehow go without a phone is a bit hard not from the point of entertainment or something but God forbid something will happen and even for help I won't call [I don't have a second phone]) service treats options finality.