Kindly advice how can I get my 4 pending salaries...

According to the given facts and for clarification purposes, we would like to explain to you,
According to the Qatari labor law:

In addition to any sums to which the worker is entitled to upon the expiry of his service, the employer shall pay the end of service gratuity to the worker who has completed employment of one year or more. This gratuity shall be agreed upon by the two parties, provided that it is not less than a three-week wage for every year of employment.
The worker shall be entitled to gratuity for the fractions of the year in proportion to the duration of employment.
The last basic wage shall be the base for the calculation of the gratuity.
The employer is entitled to deduct from the service gratuity the amount due to him by the worker.
                      
Furthermore, The Ministry of Administrative Development, Labor and Social Affairs provides this
electronic service to enable the staff members to calculate their end of service benefits.

This is in general and if you have another specific query you want to ask, please do and we will
provide you with the best legal consultation
you can file a complaint in the labor office in order to get all his rights and dues.