Short answer: You will not get what you need by just translating word-for-word. Use the following: "What" - Reword the sentence, "can" - "have the power to", "kindess" - "friend's deed". More detailed answer:

I'll use a sample sentence made up of those words: "Kindness is what I can do.". Final translation: "Fahdon sod los suleyki" (A friend's deed is my power)

To convey kindness, use "act of a friend/companion" sodsefahdon (deed-of-friend), fahdon sod (friend's deed), fahdonro sod (friend's deed).

To convey "can" or "the ability to", you can use suleyk/mul for this purpose: "He can" would be "Rok piraak suleyk/mul wah" (He has the power/strength to). You can shorten that to "Rok (los) suleykaar wah..." which is "He (is) powerful to..." (los/is is implied)

Even knowing those parts to it, the whole meaning can be condensed to the following:

Fahdon sod los suleyki ((A) friend's deed is my power) - This is because "what I can do" is similar to power. A power is something you can do. You use power to do things. As you can see, you don't need to translate the word "what" to get the meaning of the whole sentence.

Another example: "What can I do now but give kindness"? - That becomes "Is there any deed I have the power to do but to be as a friend?" That translates to "Los naan sod ko suleyki nuz wah kos med fahdon?" (Is any deed in my power, but to be as a friend?)

Hopefully this helps!