There are more weeds than grass. You have to keep it mowed and prevent them from seeding. Allowing them to seeds will just let them spread more.
You will have to either dig out the clumps or if you use a weed killer, use one for crabgrass. Make sure that you read the label and follow the directions.
Honestly, the grass is in such poor condition, it may be better to kill everything and replant. If grass is cared for and healthy it should be able to crowd out weeds. If not, the weeds take over.
Happy gardening in Hawaii. Gardens are where people grow.