"No audio device is installed" need expert help

I've had problems with backgroundcontainer.dll and resolved them by following these steps:

To resolve this, download AutoRuns and save it to your Desktop.
Create a new folder on your hard drive called AutoRuns (C:\AutoRuns) and extract (unzip) the file there.
Open the folder and double-click on autoruns.exe to launch it.
Vista/Windows 7/8 users right-click and select Run As Administrator.
Please be patient as it scans and populates the entries.
When finished scanning, it will say Ready at the at the bottom and list all entries under the Everythingtab.
In the top menu, click File > Find... and type the file name (backgroundcontainer.dll) related to the error message, then click Find Next.
Alternatively, you can scroll through the list and look for any entry related to backgroundcontainer.dll and conduit.
If found, right-click on the entry and choose delete.
Exit Autoruns and reboot your computer when done.

After I finished and rebooted pc, my audio wasn't working. I tried to reinstall drivers and it didn't work. Is there any way to revert changes I did in AutoRuns.exe? please help me...
I tried to restore too but it says there is no restore point made, stupid move by me...

If you need more info about my pc I wrote everything I know on my profile, if you need something aditional please tell me in comments + where to get that info

Screenshot by Lightshot screenshot of Device Manager

I would start by running SFC /Scannow and see if there are any missing or corrupted system files.

You listed the PC as Dell, but not the specific model. Such as OptiPlex 764, Insprion 530, Dimenson 5150, etc.

How to do scf?
Where can I check the model? This pc is few years old so I can't remember details

Click Start then Run. Enter sfc /scannow (space between c and /).

See this screen shot. Its from Windows 10, but Win 7 will be similar.