i am a student to learn unity，last week i succeeded in making a game ，but today i redownload the unity，but it just show me that
You’re trying to run an early beta of 2017.3. If you’re a student trying to learn Unity you should be sticking to the versions that have completed QA. Currently that would be 2017.1.1.
When you install a beta version you should be going in expecting some things to be broken.