keep up (something) = continue practising so as not to forget something
examples:
- If you want to keep up your English, you should read and speak in English as much as you can.
- Many people keep up old customs in the countryside and villages.
- We keep up all traditional Christmas customs.
- She keeps up contact with all her old friends.
- She keeps up a regular correspondence with her family.
- Although you are in a foreign country, you should try and keep up your native language too.
- I am afraid James still keeps up his bad old habits.
- Do you keep up your diet? I am really proud of you.
- I 'm really a nurse but it is difficult to keep my nursing skills up now that I am working as a waitress.
- It is difficult to keep your speaking skills up if you don 't actually speak the language.
