ping reply breaks from client latency high like 600-3000 ms

RouterOS Beginner Basics
1

i was running a wired network but all of a sudden the wireless ISP thing started in my city. I got a mikrotik rb 433ah with 3 sectoral 120 deg antenna, and have added almost 20 clients running on 2.4 ghz.

My problem is that on one of my sectors if 7 or 8 active clients r connecting then the ping reply from the client starts to break and the latency goes very high like 600ms - 3000ms.
When I block few of my clients which is cybercafe etc. then things come to normal like between 1-3 ms

I have heard that i can connect like 50+ active clients on each sector. Please suggest what needs to be done. Also can someone help me with configuring the rb433ah OS 3.0 FIREWALL.

2

2,4 in b? How much traffic You have on this interface (and pps)?

3

i have 4 mbps bandwidth from my isp. my clients r using 256 kbps broadband on each wireless CPE. i hv come to know that virus on the client end causes problems. how do i control that.

pls advise.