I need to understand why a telephoto lens may be important to have, because I recently returned one because I hated the focal length, short and long (the M.Zuiko 40-150mm.) What are main uses besides the obvious like nature and wildlife to use one, let's say, like in the city?

funny thing is that I haven't had a longer lens a 110mm Fov  for over a year. But now I think I should have a tele zoom, or a tele prime...just in case I have a need. I have looked at a used 40-150 m43, and a few 105-200mm MF primes, (cheaper than the m43 zoom), and a few MF tele-zooms....Vivatar 70-210 f/2.8-4 S1..

I may have a few uses a year, if my past use is the same.

The 14-150 or 40-150 are your choices. An MF prime can be obtained for much less, but MF will not only be less convenient, but will also limit your shooting abilities. BTW, M5, you should probably seek pany lenses because of the OIS.

I am thinking on the P-40-150 OIS aamof. I just have to wait till next month, and hope I can find a used one under $150.00 
I liked the 4/3 Olympus Mk1 40-150 when I owned an E-510 very much. It was/is a sharp lens almost across the whole zoom range!

I need to understand why a telephoto lens may be important to have, because I recently returned one because I hated the focal length, short and long (the M.Zuiko 40-150mm.) What are main uses besides the obvious like nature and wildlife to use one, let's say, like in the city?

Skylines and bird's eye views! It is an important part of your kit if you are trying to represent a city in images. Ok, it is not as creative as street or detail shots--either in content or perspective; I favor wide-angle "immersion" shots myself--but for capturing urban icons or showing the city in relation to its natural setting or features, it is nice to have telephoto.

Don't like the modern Olympus "collapsible" zoom lenses? Who the hell does? Somebody must, but I am largely staying away--though I was tempted by the 40-150 you are returning when you get the bloody thing for a mere $109!

Instead of the new zoom, I recently acquired an OM 100/2.8 MF for my E-P1; there is also the 135/3.5 and the super large 135/2.8. These are relatively affordable prime lenses (especially the 135/3.5) with solid mechanics.

The longer FL is difficult to handle on the LCD screen, I must admit, but I have already proven that I can get sharp photos out of the 100mm on my E-P1. I will try remember to post some photos of Oslo that I am planning to take with the 100mm to illustrate a book on the city. You might also want to check out an earlier discussion we had on E-P1.net about legacy telephoto prime lenses. http://e-p1.net/lenses/advice-requested-on-om-long-lens-for-e-p1/msg35879/#msg35879
There are other adoptable legacy telephoto primes, of course. Peterb666 is very knowledgeable on this subject and has even made modifications to legacy lenses to get better performance out of them.

Good luck , and by the way, are you interested in buying the 14-42 kit lens?

Did Panny make a 40-150?
Or is the 45-200 the only Panny tele-zoom?

also 14-140