Hello! As you are already pretty capable in English, you should be able to handle another language. I am only studying one language at the moment, so my help may not be of any benefit to you, but I'll try!
- Avoid studying two languages on the same day. So, pick certain days for each language.
- Choose one place to study Turkish, and another place to study English
- Pick specific times of the day to study your language.
I do apologise if these points aren't very helpful to you! However, these were the main points I came across when I considered studying two languages at the same time. I hope this helps a little bit!