Is there a way to speed up the blue questionmark encounters?

Blue question marks act more like a "hint direction" than anything else. From gamepressure.com:

The appearance of a blue question mark on the mini-map does not mean additional hassle. The questionnaire also does not symbolize something important. Question marks are instructed to direct you to the locations of minor investigations. Ignoring them will not result in any bad consequences. You can check out this places if you are looking for extra adventures.

A good way to track them down quicker is to scan with R3. You should be looking for a trail to follow. Sometimes these trails are marked with blood, tracks, or other signs of struggle. Also, the controller should vibrate when you get close to the minor objective, and as you walk over the trail. If you use all the tricks available to you, you shouldn't have difficulty completing these objectives, but just remember that all blue question mark objectives can be safely ignored.