Hey man. You, as an Indian, try not to try to analyze China's ideas when you discuss with your Bangladeshi friends. Because you don't know much about China.
When other countries are in danger, China will help, and this help is free of charge and does not need to pay any price. This is not only because China is one of the five permanent members of the UN Security Council, but also because it is a Chinese tradition that has lasted for thousands of years.
Of course, the extent of this help depends on how friendly the country is to China. We can't do everything we can to help a country that wants to attack us.
You can't confuse the act of helping with the act of doing business. Some of China's investment projects in many countries are helping and some are commercial. Obviously, you're confusing the two behaviors.
If you try to analyze China from an Indian perspective, you will obviously not get a correct result. Especially from the perspective of an ultra-nationalist in India.
If you want to analyze China, you need to understand Chinese culture first, and then you can get what you want.