pH is low = acidosis
pH is high = alkalosis
Think of the pH primary disturbance as a scale that goes off balance and then compensation trying to fix this, sometimes there is parietal compensation and sometimes full but never over compensation.
To distinguish between acute or chronic respiratory acidosis look at compensation of the kidneys. Compensation takes days to occur so if metabolic compensation is present then it is a chronic issue. If no compensation is present then it will be an acute issue.
Mixed acid-base disturbances can occur as well. In this case there is a primary respiratory and metabolic disturbance occurring simultaneously. This results in PaCO2 and HCO3 going in opposite direction. An examples of this would be cardiac arrest when there is both an respiratory and metabolic acidosis.