Help with speeding up MySQL

[WOLFGANGHASH]

I have approximately 1.5 million rows on my server, and there are usually around 30 concurrent users, causing a significant drop in server performance. The server specs are as follows: 3 xeon e5 2690, 4GB RAM, and SSD disk. The database is MariaDB - MyISAM. My my.cnf configuration looks like this:

```
[client]
port=3306
socket=/var/run/mysqld/mysqld.sock

[mysqld_safe]
socket=/var/run/mysqld/mysqld.sock

[mysqld]
user=mysql
pid-file=/var/run/mysqld/mysqld.pid
socket=/var/run/mysqld/mysqld.sock
port=3306
basedir=/usr
datadir=/var/lib/mysql
tmpdir=/tmp
lc-messages-dir=/usr/share/mysql
log_error=/var/log/mysql/error.log
symbolic-links=0
skip-external-locking
key_buffer_size = 256M
max_allowed_packet = 32M
table_open_cache = 256
sort_buffer_size = 8M
read_buffer_size = 8M
read_rnd_buffer_size = 4M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size= 32M
#innodb_use_native_aio = 0
innodb_file_per_table
max_connections=750
max_user_connections=500
wait_timeout=10
interactive_timeout=50
long_query_time=5
!includedir /etc/mysql/conf.d/
```

To improve server performance given these specifications and the high number of users, you can consider optimizing query performance, increasing server resources like RAM or CPU, tuning the database configuration further, and implementing caching mechanisms.