how does one get a business idea? Are there any processes/techniques

Start with a problem that doesn't have a satisfactory solution to it yet.

Work in an industry and become familiar with all the ins and outs of it. Whatever you find that has you saying, "man, this is taking forever" or "this is more effort than its worth" is an opportunity for a business.

Can you open a successful restaurant if you dont know anything about food ?

Probably not, most restaurants fail.

>>1035304
most restaurants fail even if you know anything about food

I've got lots of business ideas. And they almost all come from problems that need solving.

>>1035316
do you make any of them into an actual business?