I want to invest in bitcoin where should I invest?
You can't invest in Bitcoin like you can invest in a business.
Bitcoin is a cryptocurrency that you can buy using fiat money.
To buy Bitcoin, you will have to go through a trading platform. There are a lot of them. The best known are Coinbase, Binance and Kraken.
OKEx is a less well known platform, but it has the advantage of generally offering lower fees than Coinbase, Binance, or Kraken.
It is a serious platform that has been in existence since 2014.
If you are not familiar with it, it is worth testing the OKEx platform.
A good strategy is to create an account on several trading platforms so that you can buy Bitcoin where its exchange price is the cheapest.