Could you please tell me, how to call these things in English
N.B. monograms, ciphers, cartouches don't fit the meaning
Thank you in advance
The general term for this is scroll decoration or scrollwork. This is most often seen in architecture, on buildings that emulate classical (Greek or Roman) or medieval (European) decoration.
Specifically, your example is of foliated scrollwork:
In art history, a "floriated" or "flower scroll" has flowers, often in the centre of the volutes, and a "foliated" or "leaf scroll" shows leaves in varying degrees of profusion along the stems.
I'm not certain Lambie's answer of "whorls" is incorrect, since a whorl might be considered a subcategory of scrollwork:
In botany, a whorl or verticil is an arrangement of sepals, petals, leaves, stipules or branches that radiate from a single point and surround or wrap around the stem.
There are probably heraldry terms that might fit also. but whorl or whorl of leaves works well for your picture as two leaves come off a central stem.