How to measure available amps? Do i need more load?
Presumably you meant "MPPT" controller?
Your MPPT converter and/or your panel are suspect AND your load is probably less than fully loading the panel.

There are too many unstated factors to answer your questin well but the following should help.

What is the load?
What voltage is it rated at?
Is it capable of presenting a 200W load? 

As you say the panel is 200W rated and as 18V x 11A = 198W ~= 200W it is likely that you have quoted the panel's maximum power values.
ie Vmp = 18V
Imp = 11A.

A panel with 18V Vmp and 24V (or more) Voc has a Vmp/Voc ratio of 75% which is a larger droop that you'd expect from most modern panels.  

If an 18V panel is producing 24V at 4A it is far from fully loaded.
You do not say what the load is but if it is capable of loading the panel fully then the MPPT converter is not doing its job. 

If you fill in some of the gaps above then a better answer can be given.
Providing fuill specs and datasheet links is helpful.