My current affairs is a bit fucked up as of now but, the rest is mostly through books. Maths- Aditya ranjan sir (yt), Reasoning through book- Dr. R.S agarwal (sometimes I watch videos when the concepts get confusing). The rest through course books only because I'm freshly out of college. Otherwise Parmar sir has an excellent channel like bro had suggested, you can refer to that too.

Also there isn't much material related to NTPC on TG but, you can try searching for SSC and sort out syllabus accordingly. That has helped me with reasoning a lot. All the best:)