Is there a 5G external router that supports high speeds (800Mbps) at Mikrotik
Note the highest card is R11e-LTE6
cat 6 I need a cat12 card that supports high speeds

chateau is the only one that will have 5g at the moment, they will use different cards depending on the vendor/region you are in, have a look at the product page and under support and downloads there is a PDF with the different modules that can come with teh chateau 5g:
https://mikrotik.com/product/chateau_5g