Vincent worked at Goupil & Cie. art dealers from 1869 until his dismissal in 1876. He was initially employed in The Hague, and later in London and Paris too. Van Gogh spoke fluent English and French. His letters to Theo regularly contain advice in all sorts of areas.
Theo, I must again recommend that you start smoking a pipe.
…find things beautiful as much as you can, most people find too little beautiful.
I advised you to go out quite a lot, but if you don’t like it, don’t do it.