i give you one suggestion. Don't left the job and start the preparation of CSS and after 2 or 3 years of preparation with job give the exams because now you have 2 chance also you have 5 year till 30 year of you age. So, take your time and after good preparation take the second chance of CSS Exams.

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"wa tu`izzu man tasha'u, wa tudhillu man tasha'u"