For some period of time i know that number, i think its increased a little bit more with referral program, as its becoming more public.

Yes unsold tokens are going to be burned

For a successful start? Well a lot to get at least a share on the social market and to spread the word. But they started quite good with 40k user of the apps. It would be cool if they could get to 100k for starters.

it's a good start, but you need millions to make it viable. hopefully the number will increase soon.

Their website says more than 500k users on website but there's nowhere the more important information how many actually use the app.

It's hard to say. You could compare it with Facebook but is never going to be that big unfortunately. It also depend how active the community will be.200k is still low anyway

When I look at the Android app on the Play Store it says 10k downloads which is not much.

Marketing is very important, because there are a few competitors in their environment, even though they are a very good product, because of the marketing influence, inferior products may surpass them.

Play Store only displays a range for downloads, in this case 10.000 – 50.000.
For IOS there is no info currently.
The total number of users is 40k for the mobile app, these figures were posted last month on 7th February by Sphere_Official.

In my opinion, the total amount of the users isnt really a good indicator to be seen due to the fake users and bot
Its better to see the current user online in different hours and then averaging it.