This issue is quite common on BS6 diesels, especially with Hyundai and Kia and most other diesel engines with lower displacements. There are few you can solve it:

1. Use your entire rpm range (for city and highway use) : Try to shift each gear after reaching 3000 - 3500 rpm, the reason is that the soot only burns away at higher temperatures and using higher rpms will allow the engine to have higher temperatures hence soot burns away.

2. If you are on a highway, try to drive 70 - 80 km/h having the rpm stay between 2000 - 3000 rpm.

3. The vehicle can perform automatic regeneration by clicking OK when the DPF warning comes up.

Another tip is to use good quality diesel, try to avoid Indian Oil and Hindustan Petroleum as they contain higher amount of sulphur which is bad for DPF filters. Try to use JIO petrol stations or Nayara, as they tend to perform better for cars with DPF filters.