Is there a way to get the some data about biomass from sentinel-1 product? Then try to convert it to NDVI value. Maybe have some way to get RGB value?
Um, the Sentinel-1 sensor is C-band SAR (radar) data, not spectral. Given that NDVI is a spectral index of photosynthetically active radiation using the ratio between Red and NIR spectra, what makes you think that you can get NDVI from SAR polarisation? There is absolutely no way to derive NDVI from SAR data!
Please, go research some basics on active and passive remote sensing as well as spectral indices. In your case, even a Google search will provide a starting point.
I don't know how reliable the study results eventually really are (i.e. how well they generalize to other areas), but at least there is first empirical evidence that an NDVI approximation can be estimated from Sentinel-1 C-band SAR backscatter inputs:
Filgueiras, R., Mantovani, E. C., Althoff, D., Fernandes Filho, E. I., & Cunha, F. F. D. (2019). Crop NDVI Monitoring Based on Sentinel 1. Remote Sensing, 11(12), 1441.