one day we try to use a key for ID a fly, what a desaster
keys can sometimes be extremely difficulr ro follow. I've spent days trying to key a single species many times. Some authors can be extremely vague or presumptuous. You are not alone with failure to key a species.
Meantime, i can only suggest Nephrotoma cf flavescens (via Oesterbroek). I cannot see everything necessary to specify a positive id.