I have 12 projects and all of them seems to have the same problem:
for example project name is "Unicorn Tetris" and if i spell in search bar "Tetris" or "Unicorn" it can not find my project(but found many another tetrises variations) only when i spelled exactly project name it appears in results.
Please how to fix it?

Check out our indexing guide here, specifically the section on search: https://itch.io/docs/creators/getting-indexed#limitations-of-search

Generally speaking, it’s not worth trying to optimize for “topic” queries on our text search engine. It’s rare that people utilize the search bar for that, they instead use the search bar to find something by the name. If you want people to organically discover your project then we recommend using the appropriate tags and metadata.