Problems with Android. Please help me

From the description you have provided, it is not clear what exactly is your issue. You have stated that you have already rooted your phone.
Check if you can reroot your device. Was it working fine when you rooted it? If you have backed up your system image by taking a Nandroid backup, you should be able to restore your system to the system ROM. If not, try reroot.
Some newer like lineageOS do not come with root access. If you install such ROMs, you may need to reconfigure your root permissions. That's precisely what happens with me. After every update of the lineageOS ROM, I need to flash the superSU on my phone through recovery. That could be the case ifor you too.
I have suggestion. Check if it works for you. Go to download.lineageos.org and check if any build exists for your phone. Download it to you PC. Download latest version of superSU from the official website. Perform a clean install of the ROM. You will need to install corresponding Gapps package as well. Then install superSU. Once all the three zip packages are installed , reboot your system. Hopefully, all your issues should be gone.
Please note that senders install of ROM will remove all your personal data from your device. Take care to take a back up of your important data before performing claen install.

Please help me to re root my device. I have rooted it from king user.zip. I am not able to re root it.

You didn't mention which custom ROM you used for the new installation. Some of the custom ROMs such as MIUI, Mochi ROM and few others don't allow the root access for everyday usage. In such case they require you to manually root and unroot the device. By default it stays unrooted device. So your case maybe falling into that category.

However the device you are using shows it is rooted but root checker apps are not able to verify that. In such case try installing apps which require root access. If the default root is enabled, then the apps should not cause any issues or ask for rooting again. If the app asks for root access then you can validate that the root was not enabled by new ROM.

You can re root the device using supersu in current context. As your kinguser root seems to be failing on some parts. You can find plenty of guides out there that can allow you to reroot with the supersu.

https://missingtricks.net/replace-kingroot-kinguser-with-supersu-superuser-android-guide/

Another option in this case is find alternative ROM or default Google marshmallow ROM image and try to make use of that with supersu and go with the fresh install. That should take care of the issue.