Solution:
1.Open to create new query. type this 'ALTER DATABASE tempdb SET RECOVERY SIMPLE' with tempdb your database name. Then click execute (!)
2. Then right click on you database, choose Tasks>Shrink>Files
3. Then, on 'File Type:', select 'Log''.
4. Then, on 'shrink action', choose 'Reorganize pages before releasing unused space'. Shrink file to 1MB(depends on you). Then click ok. Now the log should be shrunk.