Hi Seyda! I'm so excited that you're learning these very unique languages. It must definitely be challenging to do both at once!
Duolingo is nice. I like it because it is very visual, especailly when you're asked to put sentences in order (i.e. the words in order to make the sentences). There is also a lot of repetition.
One app I would recommend is Mango Languages. It is a great app that has a lot of content, and I feel that the phrases you learn you would use in real life. I use it for Arabic, and it has dialiects for the different countries. I saw that it doesn't have Welsh, but you can use it for Turkish. Mango languages is also great because it includes some cultural notes about the language and people who speak it.