innodb_buffer_pool_size = 7G is dangerously large for an 8GB machine. Recommend 5600M instead. With 7G, you may be swapping, which is _terrible_ for performance. For more discussion, see
http://mysql.rjweb.org/doc.php/memory
7G would be fine on the 12GB box.
> max_connections=3000
Quite excessive, especially considering:
Max_used_connections 144
What are your clients? Apache? If so, then make sure MaxClients cannot exceed max_connections. I recommend something like 20 on MaxClients.
> show status;
That is for the one session you are running; it is mostly useless for this discussion. Do this instead:
SHOW GLOBAL STATUS;
> Table_locks_immediate | 75778
Missing some indexes?
> i found querys not using indexes as well.
If they are small tables (that will stay small), then this is not an issue.