Hi
Slow charging is a consequence of the charger and phone not communicating properly.
There can be a number of reasons and the above posts and other topics may help you decide how to proceed.
The most common causes are dirty port on the phone, not easy to see or clean.
Will find a link
The second possibility is the cable. Fully compliant USB C cables are diagonally symmetrical so that it ‘shouldn’t’ matter which way that end is inserted.
If the wiring or contacts are damaged on one ‘side’ then it will only charge in one direction or if the contacts on one side are tarnished then the charge rate may be reduced. You can re-orientate the cable to see. If it’s the same then it should be fine. Test the cable else where and try a new cable to confirm.
If you can asses the charger and cable can quick charge other devices, we are back to the phone.
The port may be dirty, so clean or at least try a couple of times
The bottom module may not be seated well or it’s contacts may be tarnished. You can remove the bottom module, check, clean and reassemble. Whilst you do that check for a red or white square. If it is not pink or red you may still have a valid warranty.
If all the above do not work you can buy a bottom module and see if that is the cause, if you use the warranty note your phone will be wiped so save any data before you send it off.
Here is a link to a post with image of the ‘red’ square and the successful effort to clean
All the best