Check grammar please!?

The mistake here is a classic split-infinitive.You shouldn't insert a word or phrase (usually an adverb) between the "to" and the verb. The most famous split-infinitive there is appears during the opening credits to Star Trek: "To boldly go where no man has gone before."

It should be "To go boldly . . ."

Though this isn't a grammatical mistake, it is guilty of uglifying English and the purists hate it.

So: "No need only to focus on one side" is the correct way of writing your phrase.

The grammatical errors are:
no space after the first full-stop (1. No need . . ) and no full-stop at the end.

No need to only focus on one side. You fogot the period. :p

There, I fixed it.

Your sentence could actually say: No need to focus only on one side. No need to focus on one side only. or could be left as you have it.

boy i don't know cos i speak patois