My company not give us a offer letter and contract...

The employer must give the worker a copy of the work contract, and if the employer refuses to do so, the worker can file a complaint with the Ministry of Human Resources and Emiratisation against the employer.
Also, the UAE labor law has set the basic working hours as 48 hours per week, and the employer can compel the worker to work overtime, and the employer must pay the worker an additional wage for the number of overtime and if the overtime hours that the worker performed at night are from 9 pm to 4 am, the worker shall be entitled to the additional time determined for the normal working hours, plus an increase of not less than 50% of that wage.
The worker can file a complaint with the Ministry of Human Resources and Emiratisation to obtain the additional wage