Good evening, how can i get the proof that i can...

According to the information provided to us in your inquiry, and according to the Kuwaiti Labor Law, Article 28
Article (28)
The work contract shall be made in writing and contain, in particular, the signing and effective dates of the contract, the amount of remuneration, the term of the contract if it is for a specific period and the nature of work. The contract shall be made in three copies, one for each party and the third shall be lodged with the competent authority at the Ministry. In the event where the work contract is not established by means of a written document, it shall still be deemed to exist and the worker may, in such event, establish his rights by all means of evidence.
Regardless of whether the work contract is for a specific of indefinite term, the remuneration of the worker may not be reduced during the contract validity period. Any agreement to the contrary, whether made before or after the effective date of the contract, shall be deemed null and void because this matter is related to the general order.
The employer may not assign to the worker any task that is not consistent with nature of the work stated in the contract or that is unsuitable to the worker’s qualifications and experience on the basis of which the contract was signed with him.
** Accordingly, the employer can refer to and review the work contract that includes all the terms of the contract to know the date as well. Once the work contract is signed, the date is considered from the date of receiving the work Article No. 70
Article (70)
The worker shall be entitled to a 30-day paid annual leave. However, the worker shall not be entitled to a leave for the first year of work except after at least 9 months of service for the employer. Official holidays and sick leaves during the year shall not be counted as annual leave. The worker shall be entitled to a leave for the fractions year in proportion with the period he spent in actual service, even the first year of service.
Article (71)
The worker shall be paid for his annual leave before taking such leave.
Article (72)
The employer shall have the right to determine the date of the annual leave and divide such leave after the first 14 days thereof, with the consent of the worker.
The worker shall have the right to accumulate his leave entitlements provided that they do not exceed two years and he shall be entitled to take his accumulated leave all at once subject to the approval of the employer.
Article (73)
Without prejudice to the provisions of Articles 70 and 71, the worker shall be entitled to a cash consideration for all his accumulated annual leaves upon the expiry of his contract.
Article 74
Without prejudice to the provisions of Article (72), the worker shall not waive his annual leave with or without compensation. The employer may recover the wages paid to him if he is proved to be employed by another employer.