I have made the biggest mistake and deleted the transaction log file. Is there a way to fix this issue? I have the backup file, is there a way to restore it or reset everything again?
Backup contains the log file as well.
Just restore the database using tsql
Restore database db_name from disk = ' path to backup file.bak' with replace, stats=10
Based on your screenshot, it seems a connection issue .. you are not able to connect to SQL server with ssms.
Also, see this blog by Aaron https://sqlblog.org/2011/01/14/troubleshooting-error-18456