Belt and tensioner replacement w245 cdi

[Exp21]

Hi everyone. My serpentine belt (w245 cdi OM640 engine) on cold starts makes squeaking noise, disappearing after some minutes and being present only at idle. I'd like to replace belt and pulleys but looking on Wis it's a real mess. You have to lower the engine to create enough room. You have two options: replacing the pulleys one by one (and I think in this case lowering the engine it's not necessary) or replacing all the part with pulleys already mounted on (see picture). Does anyone know the details of this job? Is it really necessary to lower the engine if I replace only the pulleys and not the entire "support"? I would work with car on ramps. Thank you very much, any advice is really appreciated