“something suspicious“

This line is beat to trick you into saying something that they can arrest you for. You’re only reply. Should be “OK, am I free to go?“. If they had something to arrest you for or to take you for, they would do it without asking you questions. When they ask you questions like this, they are not asking you questions to see if they can let you go. They are asking you questions to find something to ticket you for or arrest you for.

Cops are not your friends, and they are never, never, never ever ever there to help you. It is a job to fuck you as hard as possible. Do not give them that opportunity by telling them anything that would make that easier for them to do.