"Trowch i'r dde wrth y neuadd."

Translation: Turn right by the hall.

[Jonlang_]

In these types of sentences, can wrth be changed to yn ymyl or ger?

[shwmae]

Yep, those would be fine too.

[AlanThomps607735]

I typed the translation (correctly) instead of typing what I heard. When I've done this before, it notifies you, so you realise the mistake and you get a chance to do it properly. This one just marked it incorrect.