How can I fix my loose sink mixer tap?

The mixer tap is working fine , but is loose.
There is two long screws coming out from below which go into two nuts.
i have tightened the nuts , but it is still wobbly.
I have the round spanner to tighten the nuts though space below due to the sinks is not much. The screws are sticking out and wouldnt tighten.
Do the screws also need to be tightened???

Please advise. thanks