One of the special things of startups, and Silicon Valley, is that self-motivation mode of operation. You will find it in any company in Silicon Valley. No manager could tell you what you need to do, you will need to figure out what you need to do and go do it. There are usually very few written processes because things move very fast and information gets old fast too. Your first task is to improve the way you deal with people.
This has nothing to do with manipulating people but most of the jobs in Silicon Valley are communication. Although an engineer doesn't necessarily talk about it they usually have to comment out their code, write down requirements, work with other engineers to figure out who's going to do what, etc. So people may not be talking at all in the office but they will be communicating through the private channels that they have carved out.
Many people think that Silicon Valley is about computer chips and GPUs, no it's about interpersonal skills and communication.
So I think the main skill you need to learn here is how to relate to people and convey information in this type of environment. Oftentimes is the subtle skill of paying attention to people, being friendly, and being a people person. I'd start there.
People are not going to open up professionally until they get to know you.
In Europe people's relationships revolve around friends and family. In America we have to successfully deal with strangers, and this has been expertly perfected in the Silicon Valley.
Make it your business to learn to relate to the people you need to work with.
I always laugh when people start talking about GPUs, nah man Silicon Valley is built on communication and interpersonal relationships.
One of the reasons that Silicon Valley has successfully invented things is because people in the Bay Area are very nice and it's simply easier to work with nice people. None of this could easily happen on the East Coast, much harder.
This is my personal experience.