I might have the opportunity to do some contract work as a contractor in the US. My fiscal advisor already told me that I am fully taxable in my home country. I will do all the work from home. In case I would travel to the US for a face to face meeting in the context of this contract work, would this be considered working and if so would I need a separate visa next to my already obtained ESTA waiver. 

For taxation I already understood that these visits are still considered working in my home country. The cost of the trips would even be considered tax deductible as being costs for doing business.