You can take a look at the design phabricator board and see what might interest you. I suggest once you find something, reach out to the designer who is active in the thread and ask if she/he could mentor you.
Outreachy is a full-time internship program that lasts about three months. In order to estimate the appropriate size of a project, you may think of an epic task that would take two weeks for a senior designer already familiar with our projects. Such project should have already community consensus, or at least have a low risk of being contentious.
The Design backlog contains many tasks, but most of them require software development skills to be completed, and the ones requiring UX design skills only seem to be much smaller.
Tasneem, do you have a portfolio or some information about your design skills and work that might help May and other designers find a suitable project for you? Thank you for your interest in contributing to Wikimedia.