Working 16 - 18 hours per day

Depends of what's mentioned in your Contract.

Here below an extract from the Labour Law for your reference:

Part III - Hours of Work
Article 68
An employee may not be required to actually work for more than nine hours a day
and for a maximum of forty-eight hours a week which shall not include the periods
specified for taking food and rest.

Article 70
If an employee is required to work for more than the hours prescribed for in Article
68 the employer must either give such employee extra payment equivalent to the
ordinary salary to which his is entitled for the overtime work, plus at least 25%, or
grant him a permission of absence from work in lieu of the extra hours which he has
done, provided that the said employee agrees to such an arrangement.

Thank you VidoDido for your prompt reply, actually it is not mentioned in the contract.  As per the contract, we should only be working in 9 hours a day.