Hi Jasmine, from my personal experience of maintaining several European and Asian languages, I can say that a stable schedule works best. In order not to mix the languages, it is best to take small breaks between them. For example, it's easy to start mixing Spanish and Italian, but you have a wonderful Mandarin option, which can be a good switch. In general, a day for one language, a day for another, and after a couple of weeks you are automatically ready to learn one particular language on one particular day.
Don't worry, and just focus on one language in one day or hour (time doesn't matter). The main thing is not to forget in the process that learning languages is fun and interesting and not a race.