This is a question that I get a lot as a teacher. "How much practice should I be doing?"
The answer is not simple, unfortunately. Everyone's time requirements will be different. If you are an experienced practicer, and you know all of the skills (including those on my "How to Practice" page: https://www.cellos.co.uk/how-to-practice) then you'll need less time than someone who is still working things out, even if you're practicing music that is more difficult.
You may find that you have more time on certain days than others. In that case, use your time sensibly. See if you can manage two or three sessions on your empty days, but try to do at least something on your busy ones!
The most important thing is that you're playing every day, but beyond that, a rule of thumb would be a minimum of 20 minutes for everyone, 30-45 by the time you're reaching Grade 4/5, and 45-60 above that. The increase in time requirement is due to both the fact that you are probably going to be playing longer pieces, which will obviously take longer to practice, as well as the fact that those pieces are likely to have more "difficult corners", which will need a lot of repetition.
Just remember though:
Do as much as you can
Be logical in your practice and economical with your time
Maybe read a bit around the subject: https://makingmusicmag.com/deliberate-practice-is-like-the-scientific-method-for-music/ is an interesting article, but there are a lot out there.
In general, plan your practice, have clear goals, and remember that you don't have to make everything perfect in every session. As long as you've improved something, you've achieved a good practice session.