In last night dream a man who is very good at hitting the right notes and tones when singing...he invited me to go with him to a gathering where you have to be good at notes...I was singing to my self quietly...I was thinking...me too can be good if I get guidans and training...I could feel my potential...it felt good and my self confidence grew...
Pitch is physically directly tied to frequency (of air oscillation). The faster air particles vibrate, the higher the pitch. (Something like that.) Non-physically there are also frequencies. So it may be your singer was showing you how to hit the frequencies that correspond to the chakras. Music is anyway one of the closer equivalents to nonphysical transformations and communication, I guess. With guidance and training (like from this friendly being singing for you) you can indeed unfold also that potential.

I went into a building...and 2 bear cubs where playing in the elevator
Elevators can stand for changes between sub-planes, and the ability to select a particular one might mean that in that body you were in, you could navigate well and tell your position within the plane.

Pairs or triples of animals are often elementals, essentially the consciousness of each of our bodies. Depending on our wellbeing, these elementals can get quite rowdy. Or be untamed - like bear cubs - when they still need some training and care to be kept in check. They can also appears as lions, or as domestic cats, dogs on a leash, etc. This would then express degrees of control or having tamed them. Maybe you enlisted some help dealing with yours. After all, they followed you around.

In this episode I am in my appartament...a huge heap of sand is in my kitchen and a hole is digged...I can see through the hole a canal floating under and I go out...on the other side is an excavater digging in the canal...digging up shoes...I pick up the shoes and I try to communicate with the man on the excavator..he says something like...what are you doing in the building with old people
Since it's your place - maybe some past life stuff (= stuff from "old people") is being unearthed. Maybe he pointed out that this is different from you as you are now (= you are not "old people").

In general, when you are in your apartment, it is possible you might be in your own worldview, the current home of your personality within the planes. You have one on every of the planes you can access. Within those worldviews there might be all kind of material pertaining to you as a totality - the higher the plane, the more encompassing it gets. For example, past lives might have contained the karmic seeds forming events in your present life until this point, and maybe it's time their influence is unearthed. The canal might well be access to a bigger flow.

If this was your worldview and this being had access, his role was likely to help you make a needed change.

The room you found this in might also be telling. If you see a kitchen as a place to invite friends or share food with family, it might represents aspects from that body's throat chakra. Or you associate the kitchen with the familiar unit more in the sense of the heart, as in a hearth that makes a home a home. Or maybe it ties to the lower chakras - survival or even sensual pleasures. So what the kitchen represents is probably best known to yourself.