Hello Nitro123
A5 cannot be printed on both sides automatically, this is only possible with A5 as you have already found out correctly. The only suggestion is to print on the front side first, then insert the paper again and print on the back side. You can use the function "Duplex (manual)" in the Brother printer driver (useful for more than 2 pages), which "helps" you to handle the paper.
Greetings