What are the basic steps to become a building maintenance engineer?

Like all professions, the basic steps will always be to learn a trade/skills relevant to your targert industry.
Gaining experience though is and no doubt will be a different animal altogether! Having all the qualifications does not guarantee an interview nevermind employment.
I feel the other commemts have answered your question well enough for you to understand the actual skill sets generally required for building/facilities maintenance and wish you all the best in your chosen career.

you should start from point zero by going to some hotel to take training in it cauza the hotels involves all electrical , mechanical and electronically system's in it

you must have a good knowledge in Water feeding systems ,Piping, drainage,HVAC system

Education Required for a Career in Building Maintenance Building Maintenance Technicians generally learn their skills informally or through on-the-job training, though a high school diploma or the GED equivalent is highly advisable.
More advanced training from a
1- or2-year program at a technical school or vocational college should improve your competitiveness for careers in Building Maintenance.
Courses that will help you in a career as a Building Maintenance Technician include electrical systems, plumbing, science, mathematics, woodworking, drafting and basic computer applications.
Required Skills for a Career as a Building Maintenance Technician Building Maintenance Technicians should have common building and repair skills, such as basic electrical, plumbing and carpentry skills.
Being able to speak, read and write English and basic math skills will also help you in a career in Building Maintenance