Our party of 6-8 people did a day tour of La Paz, and a 3-day Titicaca tour with Cesar.  We connected on tourHQ and then on WhatsApp. Cesar speaks perfect English, and arranged private transportation (a new 14 passenger van and a boat on Titicaca). We had zero issues and he was very flexible. We ended up asking him for help for a few more things, such as hotel recommendations, additional airport pickup and drop-offs, and money exchange. We would definitely recommend him as a tour guide (and probably will as we may go back to Bolivia). He shared his knowledge of history and plants, which made our trip more interesting! Cesar himself is a trekker!