What are SAP and HSE certifications? Are they related to mechanical engineering and mechatronics?
Desire for employment in Canada is not a valid reason to study in Canada and will have you refused always. If you wrote you want to study in Canada because Canada has abundant employment, of course you're going to be refused.
You must prove you have opportunities for employment in Nigeria.
Unfortunately, because Nigeria is the source of so many asylum claims and abuses of visas, your application will be heavily scrutinized. At this point, you really need GCMS notes as you are likely always going to be refused unless you learn more the specific reasons for refusal and address them.