hAP lite in wireless station mode help

Hi,

I have following situation - ISP has its own router which provides internet access, its set at 192.168.1.1, mask 255.255.255.0 and I can control DHCP pool (currently set at 192.168.1.5-192.168.1.250). It has wifi network using same DCHP pool and all devices are working correctly in LAN and WLAN.

What I want to do? Connect this hAP lite (RouterOS 6.34.x, not sure of exact version) to wifi network (provided by ISP router) so other devices connected via mikrotik ethernet ports have internet AND they are accessible from devices on ISPs router (both wifi and ethernet).
Untitled Diagram.png
I have followed this tutorial (https://wiki.mikrotik.com/wiki/Connect_to_an_Available_Wireless_Network) and I have mixed results - sometimes they aren’t accessible from rest of network but they have internet access whole time. PC3 on diagram (actually an DVR) is accessible whole time over internet (port forward done on ISP router) but PC1 or PC2 sometimes cant access it locally (ping not working). Also, Mikrotik is completely inaccesible (tried Winbox discovery) and its IP is set to 192.168.1.254 (should be, but I cant access it). Its not a wifi issue since this PC3 (DVR) has internet access whole time and I can access it remotely even when local PCs (1 and 2) cant.

PCs 1 and 2 have DHCP assigned addresses and they see each other, have internet access entire time…

What did I miss?