Yes, I know it very well, I live on Russell Square - good area! :)
You are staying at the Tavistock, I assume?
It's a very popular area with tourists. Of course make sure to visit the British Museum. There is a lot to see there and I even pop in every couple of months. My favourite sections are on Assyria, the Nereid Monument and the Mausoleum of Halicarnassus. I recommend not going during the weekend because the queues are massive. If there is a big queue, go in from the back entrance on Montague Place, the tourists don't know about it and there is never a queue. Then as you are leaving come out from the main entrance so that you can see the facade, which is impressive. For a quick bite there, I recommend okonomiyaki at Abeno on Museum Street (right in front of the museum main entrance) but they are busy so you normally need to book in advance (as a general rule, in London, everything during the weekends in particular needs to be booked in advance). There is also a nice pub in front of the museum with Neck Oil on tap.
It is kind of difficult to recommend things to see and do in London because it really depends on your interests. It's not a small town where you have an obvious bucket list of things "to do" which are all within walking distance. I cannot comment much for football - I have only been a couple of times many years ago and my friends gave me the tickets - as I am really not interested in that. Broadly speaking, there isn't much to see in those areas and I would stay away. The matches are mainly attended by the British working classes / oiks, who are basically swine, so do watch yourself.
I would recommend a trip to Soho and the Chinatown - well worth seeing in their own right. You are likely to get carded, but if you manage to sneak in, I would recommend a cheeky drink at Opium or Experimental Cocktail Club on Gerrard Street. Neither have signs outside and can only be accessed via nondescript doors (Opium has a more distinctive green door). If they don't let you in, you are more likely to sneak a drink at a pub. These are aplenty so wander until you find one, especially ones with lots of students. In the area where you are staying, The Queen's Larder on Queen Square is my local but it does have a more distinctly elderly atmosphere to it (which is probably why I like it). For a more youthful setting you probably need to head to Shoreditch to try the clubs and bars there.
If you give me more of an indication what you'd like to do then I can narrow it down a bit more, but more broadly everything is readily available and can be found at your fingertips (i.e. your smartphone). I would try cuisines you wouldn't necessarily be able to find in Russia. Special shoutout to Assenheims 56 - worth going for a single meal to try the grilled chicken with the green sauce (which is divine - and it's dirt cheap. For more upmarket places, these can really go either way because a lot of them are obnoxious and overhyped, but quite recently I went to Simpsons on the Strand and I was quite happy with that. Galvin La Chappelle is also in a nice setting (again, need to book in advance, for the former make sure you ask for a booth).
Hope you enjoy your stay. It's my favourite city in the world and I am sure you will have fun, but it can be kind of difficult to navigate for a tourist because the culture is not outwardly open. It's more of a city for living than visiting, though, but if you have money you can have a terrific life there.
Hit me up if you have any more questions :)
Also, again, if you manage to get in, Reverend JW Simpson on Goodge Street is terrific for cocktails and they have a cracking playlist. Again the entrance is kind of hidden so look it up in advance and keep your eyes open.