English Me
An online app from the creators of the renowned portal Help for English offering a huge learning database of over 500 hours of grammar tests (focusing on simple grammar as well as advanced tricky points) with explanations in Czech, tens of thousands of vocabulary items with example sentences, pronunciation by British and American native speakers, diverse activities and much more. You can use it to learn at your own pace and focus on what you are interested in, what you are doing at school at the moment, or you can let the app lead you. Try a week for free, no commitment.