I now have managed to move dynamic objects using a touchjoint on screen. When they collide with other dynamic bodies they change their path, like the other bodies do.
My question: Is it possible to somehow let the moving body (the one we move by using the touchjoint) just push away other dynamic bodies without changing it’s own moving path during a collision? Like a tank pushing away all other stuff without getting slowed down by the stuff? (Does this make sense?) 
“without changing” at all? no, dynamic bodies are affected by collisions, both ways. (aside: a kinematic body won’t work for you either, as by definition they don’t respond to forces, including touch joints, so it’s a non-starter)
a tank works because it’s super-massive relative to the stuff it’s brushing aside, so receives relatively little of the reaction force. that’s the real-world model you should try to duplicate with box2d. try just making your touch-jointed body extremely massive relative to the other bodies. (and up the touch-joint force accordingly to compensate for “feel”)
Thank you for your quick help!
Regarding the touch-joint force: I actually just use a normal “movement” like for example I add x=x+1 and y=y+1 to the touch joint position, so it is pulling the physics object in a direction. This is not exactly a “force”.
Is there another way to still have control where to move the object exactly on screen (exact coordinates) with forces?
a touch joint works on a body by applying a force, it doesn’t matter “how” you move the touch joint’s position.
but given the way you’re using the touch joint, you could potentially eliminate it, allowing you to use a kinematic body instead (see my “aside” comment above)…
each frame simply calculate the velocity needed to reach the target position in the desired time, and set the body’s velocity directly - which you can do with a kinematic, you just can’t apply a force to produce that velocity. kinematic acts as if infinite mass, so is unaffected by forces, including touch joints and collision response.
so,… having ditched the touch-joint requirement, that would seem to be exactly what you want: a moving body that won’t respond to collisions.
Thanks for your detailed help!
“without changing” at all? no, dynamic bodies are affected by collisions, both ways. (aside: a kinematic body won’t work for you either, as by definition they don’t respond to forces, including touch joints, so it’s a non-starter)
a tank works because it’s super-massive relative to the stuff it’s brushing aside, so receives relatively little of the reaction force. that’s the real-world model you should try to duplicate with box2d. try just making your touch-jointed body extremely massive relative to the other bodies. (and up the touch-joint force accordingly to compensate for “feel”)
Thank you for your quick help!
Regarding the touch-joint force: I actually just use a normal “movement” like for example I add x=x+1 and y=y+1 to the touch joint position, so it is pulling the physics object in a direction. This is not exactly a “force”.
Is there another way to still have control where to move the object exactly on screen (exact coordinates) with forces?
a touch joint works on a body by applying a force, it doesn’t matter “how” you move the touch joint’s position.
but given the way you’re using the touch joint, you could potentially eliminate it, allowing you to use a kinematic body instead (see my “aside” comment above)…
each frame simply calculate the velocity needed to reach the target position in the desired time, and set the body’s velocity directly - which you can do with a kinematic, you just can’t apply a force to produce that velocity. kinematic acts as if infinite mass, so is unaffected by forces, including touch joints and collision response.
so,… having ditched the touch-joint requirement, that would seem to be exactly what you want: a moving body that won’t respond to collisions.
Thanks for your detailed help!