I guess you mean the "Home feed", i.e. when you open https://www.researchgate.net being logged in. It seems that the possibilities to control this are very limited. Currently, you may follow or unfollow other RG members, and this has an influence on the "Home feed". Perhaps your profile settings (especially the indicated "Disciplines") also have an influence, but there is no information how it works exactly. The only very short information on this feature is at https://explore.researchgate.net/display/support/Getting+started : "Your home feed is where you'll discover the latest research and other updates from your network. Simply click Home at the top left of any page to get back to your home feed."
Thank you, Wolfgang! Yes, I was asking about the Home feed. It's unfortunate that we don't have control over preferences. I checked my settings, and I'm certain that I never indicated any preference myself. I couldn't find the Disciplines setting either. It's just I noticed that I started to receive updates on a particular author who does research in microbiology. Since my area is Linguistics and I have no interest in microbiology, I don't really understand why this happened and how to stop it.
When you open your profile (https://www.researchgate.net/profile/Vladimir-Kulikov), there is a box titled "About me". Click on "Edit" and then on "Edit disciplines". After you will have added your discipline(s), the home feed may be more precise. But as RG is a block box and we do not know the principles of their algoriths, this is just my assumption.