Hi @connieliu! Welcome! Yes, please post a draft proposal here and someone will review when they can. Just try to leave enough time before the deadline for folks to respond and for you to have a little time to edit after.
Saber posted some example proposals in this thread: GSOC Example Proposals that may be helpful. It’s good to be specific when you can to show that you can take on the work, but it’s ok to keep things a little flexible and to expect goals to change based on user input, etc. Or, if you need to do some research as part of the project, you can account for this in your timeline.