I worked at Google as a Software Engineering Intern in Summer 2017 before going for the full-time role. The interview process for cold-hires involves application filtering, a technical phone screen, then five on-site technical interviews, each 45-60 minutes long.

For interns, the only extra work required to apply as a full-timer is two on-site technical interviews, each 45-60 minutes long. Luckily, you're already on-site; they will interview you while you're still interning. Mine were down the hall.

They then look at your work performance as an intern and reviews from team members and your project host to determine your acceptance.

The questions are technical algorithm challenges. Study up on your computer science digs; there are plenty of resources online.