I want to practise my speaking skills in Russian but I have no conversation partner knowing Russian pretty well to correct all my mistakes. What should I do?
My approach has always been to increase input - this will automatically improve your output without you having to make a conscious effort.
In practical terms it means increasing your exposure to the language and culture in any possible ways, i.e. passive listening and watching as much real life material as you can without making any effort to actually understand and parse what you hear and see.
It is important to relax, and not set the goal to actually understand everything, but rather open up to the linguistic and cultural stream and absorb the patterns and the frequencies, exactly like you did with your mother tongue.
Hearing something and not being able to understand it makes most people uncomfortable, they often give up and quit, because we tend to invalidate ourselves and our abilities when we don't see immediate results.
Most people don't realize that passive listening with relatively low percentage of decoded information is in fact progress.
While a child will keep listening and absorb the linguistic input even if they cannot decode the data, adults will typically shut off and block any input simply because they might have a strong idea that "I don't understand" or "It makes no sense" - this is a BIG way in which adults are different from children. Children don't judge themselves based on immediate results - although of course they eventually learn to do it as part of their 'education'.
Paradoxically, but the adult ego can completely block knowledge and skill acquisition for the sole reason that it does not get visible and immediate gratification. This is a byproduct of our Pavlov-dog-based gratification education system and can block people from any kind of learning process which does not give instant results.
Once you overcome this purely psychological barrier, you'll be able to watch/listen original material without the need to understand it all, and without invalidating and blaming yourself for not being a genius.
If you keep up your regular exposure you'll inevitably see results - it might take longer than you originally expected, but as a reward, your output will become natural.
Let your 'subconscious' do all the hard work!
PS. There is widespread belief that access to a native speaker can give you a significant boost with a foreign language. In my experience this is not the case — while it is definitely very useful, the efficiency is quite low, especially when the native speaker is not an experienced professional teacher, and you both have a fallback language. Of course, a native speaker will provide you some exposure, but won't provide enough exposure to cause a qualitative boost. A trip to a foreign country is way more efficient, since this is exactly the case when your survival depends on being able to communicate in that language. But again, the existence of a fallback language can "ruin" the experience.
In addition to the accepted answer here,
I'd also suggest checking Conversation Exchange, which helps you connect with other people learning the same language as you across the globe. Here's the page for Russian (if you sign up and download the mobile app, you can have voice chats to improve your pronunciation in Russian).