The CGP GCSE French workbook is great for practicing, especially the translations, as you can test yourself on vocab, grammar and translation all at once! Other than that, HelloTalk is good for practicing conversation (as long as you keep general internet safety in mind) and lawless French (website) is good for getting your head around grammar! I'm not hugely keen on duolingo, tbh, but it's ok for days when you can't or don't want to do any proper French work!