How to make vanilla forum more secure?

Hello guys. Do you know what will make my forum more secure? What should I edit in my nginx? Or php.ini? I only add this line and IDK if it help or not
disable_functions =exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source
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Any tips and tricks please?