There are two different Lenovo Vibe C (A2020a40) official firmware packages available in this post. The first is for Single Sim (SS) version while the second is for Dual Sim (DS). Please take note of this before downloading.
As always, we advice that you notify us if any download link is broken so we fix it (them) ASAP.
How to flash
To flash this firmware, please follow he instructions available via this link, click here.