If I work less than a year (6 months) and I earn 26,000 per annum. However, I didn't work before, therefore in March the overall amount will be apox. 13,000. Am I entitled to the tax return as they deduct the tax off my salary monthly?
The amount of taxes withheld in a period will be based on your income for the period extrapolated out to an entire year, and taking into account the number of allowances you claimed. So if you only work 6 months, and have no other income, then your total income for the year will be less than what your wihholdings were based on, and you probably will get a refund.
However, you won't know for sure until you actually file your tax return and calculate the amount due taking into account all deductions, exemptions, credits, and wihholdings. It's possible that you claimed too many exemptions on your W-4 and had less tax withheld than you should have, and would then owe tax when you file.