I think the tips and notes for this section should make it clearer this tense is for 'I have gone' etc rather than to say 'I went'.
The notes says that 'dw I wedi...' is comparable to 'I finished'. The answer here suggests it's closer to 'I have finished'. Is it both?
'Dw i wedi...' is technically the present perfect tense, which translates to 'I have...'. So, 'I finished' would be something else, as it is the past tense.
why is I went wrong? isn't that the same as I have gone - no-one says I have gone to Shrewsbury yesterday they say I went
"I went" is a different tense. It's "es i" in Welsh, but "mynd" is an irregular verb and I'm sure you will come to the rest of the forms as the course progresses.
This is a good question--and you should not have been voted down. I have but one upvote to give you, putting you back at 0.
The question form of Dw i is usually Ydw i?, so "Have I gone" is Ydw i wedi mynd?.