How can I avoid jamming in the feeder? Recently, at work we bought a Guider II printer from FlashForge.
When we try to print models using a high resolution or models with a too high printing time, the feeder gets clogged. And the feeder is too hot. We have concluded that the feeder is getting clogged because the high temperature softens the PLA.

We check the feeder fan and is working fine. How can I avoid the jamming? Pausing the 3D printer and wait a few minutes is not working for us. I don't know if it is a common problem for this 3D printer model.

Edit: 

The hotend is an all metal hot end. I can't find more information about the hot end. 

In the manual of the guider II flashforge recommend a temperature of 210°C for the head and 30°C for the bed. I have tried different temperatures. The most common temperature I've used is 190°C for the head and 55°C for the bed (I obtain the best results with this temperature).

This is the Hotend used by this 3d printer.
The symptoms you describe hint to heat creep. Heat creep is the gradual increase in temperature of the cold end assembly (cooling fins and heat break). This gradual temperature increase leads to too high filament temperatures and as such premature filament softening. In combination with (large) retraction settings, this can lead to clogging of the nozzle. All-metal hotend assemblies are more prone experiencing these problems; lined hotends have a PTFE lining that also insulates the filament so that it does not soften prematurely like in all-metal hotends can happen. Heat creep is best remedied by properly cooling the hotend (good quality fan, no obstructions or large ducts) and reducing the retraction length (and possibly lowering the print temperature, but you already tried that). You could also contact the manufacturer for advice.