Car feels like brake is on. Serious loss of power. MPG down a third. HELP!! Is this just the difference between mile-high & ocean-low?

My car has a permanent "engine service on" which I do notice when I speed the there is loud roaring noice from the bunnet engine.
Second is that I notice the car is consuming very high fuel.I had my airfilter changed,oxygen sensor,valve but the fuel consumption is still poor and not economical at all.

how can i change my car language from french to English
your answer will appreciated

My infiniti started on its own when I was locking the doors and was unable to turn off.