Your best source of help at this point is this forum. Pine64 does not currently have the kind of resources to take in your unit for testing, I don't think. You would be better off buying a new one. But first, let's get the one you have working.
Fortunately, it seems that you are having a software problem, and one that seems to be commonly reported with Manjaro. What you'll need to do is install Manjaro or some other operating system on an SD card, with which to boot the Pinebook Pro. I recommend the Debian image that was originally the official operating system, rather than Manjaro. But Manjaro should really work, too. Go to the Wiki linked at the top of this page, to Devices -> Pinebook Pro -> Pinebook Pro Images, and download either the Debian Desktop or Manjaro ARM image. Then you'll need an appropriate micro SD card, and a way to write the image to it.
Let us know what operating system you have on the computer you intend to write the SD card with, and we can tell you how to do that.
This may seem tedious and undesirable, but really this is the best possible way to learn what you're trying to learn.
It's also possible that someone can walk you through how to fix your current Manjaro installation the way it is. But I think you're better off booting from a micro SD first. You should have this ability anyway.
Fortunately, it seems that you are having a software problem, and one that seems to be commonly reported with Manjaro. What you'll need to do is install Manjaro or some other operating system on an SD card, with which to boot the Pinebook Pro. I recommend the Debian image that was originally the official operating system, rather than Manjaro. But Manjaro should really work, too. Go to the Wiki linked at the top of this page, to Devices -> Pinebook Pro -> Pinebook Pro Images, and download either the Debian Desktop or Manjaro ARM image. Then you'll need an appropriate micro SD card, and a way to write the image to it.
Let us know what operating system you have on the computer you intend to write the SD card with, and we can tell you how to do that.
This may seem tedious and undesirable, but really this is the best possible way to learn what you're trying to learn.
It's also possible that someone can walk you through how to fix your current Manjaro installation the way it is. But I think you're better off booting from a micro SD first. You should have this ability anyway.