how much to fix iPod 5th charging port?

Apple doesn't fix parts as much as they exchange the device for a refurbished replacement

Apple - Support - Service Answer Center

might give you the price (it's in US dollars so not sure if the link will work for you) but 5th gen out of warranty replacement costs range from $99 to $149

now if your device is still under factory warranty and it's determined that the error is a manufacturer's defect, the replacement could be free. the only way to know for sure is to make an appointment at your local apple store and talk to them

A third-party place like the following maybe less. Google for more.

iPhone Repair, Service & Parts: iPod Touch, iPad, MacBook Pro Screens

Replace the connector yourself if you are up to it

iPod Touch Repair – iFixit