PostGIS Intersects Query takes lot of time to get the result
I suggest to calculate the intersection of the geometries beforehand only once and store it in an additional table evidensapp_seniangcbr_polystructures_intersection containing an id, evidensapp_seniangcbr_id pointing to evidensapp_seniangcbr.id and evidensapp_polystructures_id pointing to evidensapp_polystructures.id.

Then you can get rid of the geometry intersection in

INNER JOIN  evidensapp_polystructures ON ST_Intersects( evidensapp_seniangcbr.geom ,  evidensapp_polystructures.geom )````


and instead use a join using the ids

INNER JOIN evidensapp_seniangcbr_polystructures_intersection intersec ON evidensapp_seniangcbr.id = intersec.evidensapp_seniangcbr_id 
INNER JOIN evidensapp_polystructures ON evidensapp_polystructures.id = intersec.evidensapp_polystructures_id


Off course this only works, if your data does not change. Otherwise you need a trigger doing the intersection and filling the evidensapp_seniangcbr_polystructures_intersection table.