I intended to add absolutely the same words as my friend @madlenfox did.
Located at St.Petersburg, love the city, have rather fluent english and be extremely happy to guide you - at least a few days, to a few locations, and provide you with some info.

I mainly concerned with its history, its architectural follies and beauties, its myths. I am not too bothered with its modern life, so probably cant provide you with super actual info 'where to eat' and the sorts :)

I do know three good steemians who share with me this place. I would pray your plans work well and you be able to make way from Helsinky to Piter (yes, I prefer using this unofficial name too!). A little steem-meetup will be inevitable, then, hehe. All the best!