Having grown up in Wales, I can't say I've been having the same issues with grammar as opposed to just raw vocab, but, all the same: I'd keep at trying to learn Welsh, the rules aren't completely random - you'll get there eventually!

I will suggest though, that you might find it helps a bit to backtrack up the tree, and redo some of the easier units to really reinforce what's going on grammatically in them, rather than surging into the harder units which are far less polished and tested.

*Dw i fynd is also wrong.

• Dw i'n mynd, dw i wedi mynd are correct. So are:

• Dw i newydd fynd - I have just gone

• Dw i ar fynd - I am about to go
• Dw i am fynd - I want to go/I am going to go

Perhaps Duo forgot to type the newydd/am/ar or something similar.

The lack of Tips and Notes sections leads one to think that Welsh is like the game of Fizzbin, from the Star Trek episode "A Piece of the Action," with rules made up on the spur of the moment simply to confuse the learner. You guys have been wonderful at clearing up the confusion in the comments section, but I am growing weary of having to guess at the grammar. I may simply do Swedish or Chinese (on another platform) and come back after a few months to see if any actual grammatical rules have been added.

A good grammar book such as 'Welsh Rules' (by Heini Gruffudd) might be helpful if you feel the need for more structured information than the Duo approach offers.

Er... yes. (Trying to think if there are exceptions...!)

Well, it's that other one, at least, such as Dw i fynd.

No, I simply forgot the yn.

*Dw i'n fynd would also be wrong - nothing to cause a mutation.

Yeah, I'm finding Welsh too enjoyable to set it aside for long. It is far more exotic than a Romance, Germanic, or Slavic language, but much more familiar than a non-Indo-European language, like Turkish, and one does not have to learn what is essentially an entirely new pronunciation for every letter, as in Irish.