I have a gigabyte brix pc
Gigabyte have made more than one single Brix pc, so which exact type are you referring to?
Uploading a kodi.log file to Pastebin.com - #1 paste tool since 2002! will also help a bit.
As already said, we have no clue which Brix unit you have. Our crystal balls are away being polished which probably does not help. 
Generally for an Intel NUC or similar box (such as the Brix range) no special resolution settings are needed. And you can't just add drivers to LibreELEC anyway - it's built as a complete system with needed drivers included.
If you don't have 4k resolution as an option in the LibreELEC display settings then it's perfectly possibly that your unit is using an older CPU with older graphics hardware and does not provide support it. It's also possible, but less likely, that your TV doesn't report its resolutions correctly. Lastly, are the TV and Brix directly connected, or is there an AV receiver in between? If so then that would also need to support 4k pass through.
So the processor is an i3-4010U - thats a Haswell family processor, and the graphics within is Intel HD4400. I think that makes it just about the first Intel embedded graphics to support 4k over HDMi. My guess (and I am no expert) is that given the somewhat variable support by Intel for the Linux drivers for their graphics hardware, that early generation may not be as well supported as the more recent ones. By way of comparison, I run a Celeron N3060 platform - that's not a Brix, but an MSI Cubi N, so a similar concept. The N3060 is a Braswell processor with HD400 graphics and was launched two and a half years later - that works pretty well with 4k h264 encoded material.
I will allow others to comment, but it may just be that the Linux drivers from Intel are the problem here.
Could be a kernel bug. Or driver bug. Some Intel hardware is unable to access higher resolutions under Linux. Don't know why for sure. Take this example: LibreELEC Testbuilds for x86_64 (Kodi 18.0)
Filing a bug on Bugzilla Main Page might be your best option (file it under Product=DRI, then Component=DRM/Intel).
Be sure to submit a full dmesg with debug by adding "drm.debug=0x1e log_buf_len=1M" to the kernel command line.
You can either connect an external DVD drive for the installer disk, or create a bootable Windows 10 USB installer stick/pen.
After that, it's up, up and away.
You need to be a little more clear on what it is you now want to do.
As per specifications. the maximum output is 4K@24hz for the Intel HD 4400 graphics of your Brix box, so you will need to connect a TV for that setting. A typical 4K PC monitor will not support 24h. Are you using a TV that can do 4K 24hz? If not, then it's no 4K for you.
Why your Brix is not fully responding, we don't know. We need a debug-enabled kodi.log file from your Brix for that.
but how can i go back to installing windows 10 on my brix?
How to re-install Windows 10 onto your Brix is really beyond the scope of this forum. I hope you can understand us forwarding you to the nearest Windows support forum.
