I'm a career switcher who was given not very challenging tasks at my first tech job. The first day of my second job, I was thrown into a new language, framework, and codebase and given (what I thought at the time) was an impossible task, and no one else worked on the project. I remember just sitting at my desk thinking I should quit. That there's no way I would be able to do this, so why not quit before I was found out. Luckily, I took a deep breath and told myself I would just try my best.
2 things have always helped me when I feel like an imposter:
Breaking things into smaller tasks. When something seems too hard, I try and make it into tasks that I can accomplish one by one, which gives me more confidence as I complete each.
Helping people. Whenever I think I know nothing, I answer someone's question and while I'm explaining something, I realize that I do know things! You can try this technique to explain things to anyone. Just talking through anything makes you realize you know more than you think.