Do you have any advice for learning Welsh, in particular Welsh grammar??
Everyone is different, and will have their own way of learning, but my advice would be:
1. Avoid Duolingo like the plague. It's not worth it. I'm pretty sure lots of the Welsh course is AI generated these days too?
2. SaySomethingInWelsh is a great resource for me personally, though it only teaches you spoken Welsh, and it's not free. I tend to do a lesson a day in the morning while I get ready
3. If you're in Wales and can access the Welsh lessons run by the Welsh government, those are really good too! (I think maybe you can access them if you're not in Wales too actually, but I'm not sure about outside the UK)
4. Talk to Welsh speakers! Most are very happy to practice with you and help you learn and will be able to answer questions about things like grammar! SaySomethingInWelsh also has a forum for this if you go down that route
5. Immerse yourself in the Welsh Language. This can be harder if you're not in Wales, but Welsh TV, books, radio, music, theatre, etc can be a great resource and I think there's even books and TV specifically aimed at helping you to learn. Tumblr blogs like @textpostscymraeg are really useful too!
6. Most of all, it's just practice. Learning a language is hard, and it takes many years to become fluent (I'm still very far from being fluent myself), but the best way of practicing is taking the plunge and trying to speak in Welsh with other Welsh speakers/learners, even if it's scary :')
Hope this is helpful :) Feel free to ask me if you have any other questions!