Who can move first in this situation?

You answered correctly: in this situation, you can move first.

Here’s why: When turning or entering a priority road from a side road, you must always give way to vehicles already on the priority road. In this scenario, you are on the main road (indicated by the curved main road with the tractor also driving on it), while both the red car and the blue tractor are coming from side roads or are about to enter or cross the main road. Because you are continuing along the priority road, you have the right of way and may go first.

Remember, when following the priority road markings, all traffic already on that road—like you—has priority over vehicles coming from side roads. This will help you correctly judge similar situations in the future.