Some suggestions, depending on your context:
- Problematic describes something that is constantly a problem.
Example: "The situation was problematic for the teachers".
- Demanding describes something that requires a lot of your attention.
Example: "I do a very demanding job".
- Involved can describe something that is difficult to understand or complicated.
Example: "My job is very involved".
- Elaborate describes something involving many carefully arranged parts or details; detailed and complicated in design and planning.
Example: "The instructions are extremely elaborate".
These are just a few examples. You could also use "complicated" or "complex". Perhaps use an online thesaurus to look up some synonyms of any of these suggestions.