A German friend told me about an app she found that she was using to build her English vocabulary. It's called Magoosh and she was very enthusiastic about it - you probably haven't seen any Magoosh reviews, so I made one myself!
Here's a 10-minute video in which I review two of the free apps they have made.
Let me know if you find the apps useful or not!
The following link is another resource that might be useful - it's a huge site full of English teachers and learners around the world. You might find a language exchange that suits you, there are lots of posts from English teachers, and discussions between learners. Take a look!