Since St.Petersburg is visited by over 7 million tourists (of which 3.5 m foreigners, most of which package tours) picking the right tour guide can be tricky. I was lucky to find Valeria of St.Petersburg Guided Tours (not to be confounded with similarly named Tour-in-StPetersburg). I booked a 3-day private tour and everything went smoothly and as promised. The communications by by email and also by WhatsApp during my visit was rapid and efficient. I wanted to see Moscow after my 3 days in St.P. and she advised how to get there best (by Sapsan high speed train) and booked tickets and seats for me since international reservation on Russian Rail did not work. Also, Valeria showed flexibility according to the weather and knew how to skip long queues of mass tourism.
A memorable experience I can warmly recommend to other individuals or small groups. I wish Valeria much success with her small sympathetic enterprise.