When working in area, where there is plenty of electromagnetic devices, and much of metallic elements around
what setting can help to improve signal?
at least some...
Are you talking about regular clients connecting to your AP or about a PTP/PTMP deployment?
For the latter I'd recommend lowering the channel width to the absolute minimum.
Make your antennas as directive as possible.
RF rear shields prove to be pretty efficient in my experience - use them on sectors to filter out noise from rear and partially sides.
Also ceramic filters in the cable path between antenna and APs are a very good choice (as close as possible to the antenna) - the drawback of those obviously is that you have to stick with the selected frequency until you change the filter.