Maku, you might take a look at the Room Analysis Primer Sticky. It needs updating, so do a search on one speaker or two? I don't think curves such as these tell much without context. One speaker or two? One mic position or an average of many? Software such as Fuzz, REW, and ETF are however extremely useful to show the effect of changes. e.g. move the speakers closer to the wall and measure again.
Room treatment always works wonders. Check out the 'how to' articles at GIK and RealTraps. DIY stuff at
studiotips - tips on studio design, acoustics, and wiring. Very simple stuff. BassTrap the Corners extensively, Cloud overhead, and RFZ. Do that and your curve will flatten considerably. I like the downward trend towards HF.
Mixing in a room with such a response tends to translate well to the outside world.
DD