May I know any blogs/websites with a focus on China companies and evaluations ? Looking to invest into these China companies for a long (10-20 years) horizon so I want to learn and educate myself.?

Maybe The Motley Fool Hong Kong will be a good start.

Alternatively, you may want to pay for a subscription service by Dr Wealth called, Growth Dragon Newsletter, which provides a watchlist of China stocks that you can invest in with a margin of safety, and the analysis for each proposed investment.

Top idea. difficult field.

I'd recommend China ETF investing, and ultra-longterm as you plan is super.

Even when ad hoc news rarely serve the investor, I love this blog:

https://chinalastnight.com

reading on the website of top U.S. based China ETF company is also nice, I love some of their technology ETFs (KWEB, KURE; there will be even started a SSE Star Market 50 Index ETF, which then of course is quite risky)

https://kraneshares.com/