Hi, sr. My name is Gustavo and I am a Structural Engineer from Brazil, next to Chile. I´ve checked your project description and the attached files. I noticed that you don´t have the architectural or original structural projects, so to deliver a professional project we will need to stay in contact, so I can be able to make questions about the existing structure. And for that, I will require first, a handmade (sketch) of the walls, columns, and beams (ex: floor plan made by hand), with sizes and positions to estimate if the roof balcony will hold the load to people be there. For the steel frame, I suggest to build with its own columns and footings (separate from the existing one), so I will need outside pictures for interferences and to choose the best place to design it with least interference in the landscaping. In resume, that will be the project.
In my experience, that kind of project takes longer and has more work to do than a project started from zero, so, my suggestion is that we work with an hourly rate, based on a freelancer milestone released at some steps that we determinate beyond the way. And my time frame will be shorter on longer, depending on the timeframe of the answers about the build and field that is already there.
If you want, I can deliver a previous work sample too. And I hope that we can talk in english, because my spanish is not well to conversate, but well enough to develop the project in the Chile standards.
Kind Regards;
Almir Gustavo
PROTEC