Looks like your multi-gauge is an Asian reproduction. They are supposed to work with regular VDO senders.
The senders work by providing different resistance to ground, depending on fuel level or temperature, respectively.
If you go to each sender, remove the wire from it and ground the wire to something either under the hood or on the engine, the respective gauge needle should go from zero (left side) to full scale. When you remove the wire on the fuel sender or engine sender from ground, the needles should return to zero. You will not break the gauge by doing this (it's how they are supposed to work) and it will tell you if the gauge is working properly. I suspect it is, and you have a sender issues as Bill mentioned.
Once you know that, then we can probably help you with the right senders (in a confusing way, of course!) 