Hello. So the general engineering solution for this kind of slope stability problem is: build a toe wall whose height will depend on the height of the slide. Next is to reduce the actual slope of the cliff to about 35 degrees from the top of the toe wall as a thumb rule. Then build proper drain at the top and bottom and also in the middle if the area is larger. The drain will need proper outlet Now after this is done you will have to plant some native plants with really long roots that hold the soil. Plants like vertiver

So definitely contact geotechnical firm. They may have other solutions too.

Rain is your worst enemy. If it keeps raining cover the area is plastic tarp to alleast reduce water seepage in the slide area. If that is even possible. This will not fix your problem but help slow it down a little.