Three basic questions from a Munich newcomer

So I've got a few queries which have built up over the last weeks and wouldn't mind getting solved.

Firstly, can you buy light bulbs in supermarkets in Germany (Aldi or Lidl)? If not would a place like Hertie do (ideally it'd be a selection of energy saving bulbs)?

Next I've seen a few of what appears to be security guys wondering around this area. They last lot was the other day and they had a fairly large dog between them and had something along the lines of ELH security across their jackets. Are these guys police or something else (and what happens if they choose to address you in the street) - my assumption was that they may be some kind of building guards?

Along similar lines what exactly is the purpose of the guards that hang around the UBahn station every so often (can they arrest you or demand to see your ticket?)?

Finally I've noticed a build of white deposits all over my sink and toilet which I guess is due to hard water. Is there any specific product I should be looking for to prevent build up (like say a heavy duty bleach for the toilet) or tools to be used?

Also to clean tiled and lino floors should I be looking for a mop and bucket and special cleaner (again would this be available in Aldi or Lidl if looked for hard enough) or would soapy water and a cloth do the trick?

Lidl has some lightbulbs but not all kinds. Hertie should have them, you could also try a store like Rewe (they have a better selection than discounters like Lidl and Aldi), or a Baumarkt (like toom)

Can't answer your question about the building guards. They are not police, though.
The U-Bahn guards can ask to see your ticket, yes. They are also private security personnel. I don't think they can arrest you, but probably they can detain you and call the police if you cause trouble. Or they might just escort you out of the train/station. I personally am very glad that there is so much security on the U/S-Bahn, makes me feel a lot safer, especially at night.

Munich has hard water, so I assume that is what it is. What you want to be looking for is Kalkreiniger. Any drugstore should have it.

I personally use the Swiffer wet to clean tiles, but I think that is pretty much up to you. Do you like sitting down and scrubbing the floor, or do you prefer the more comfortable method...

I just googled Linoleum reinigen (to clean), and I got a site saying you use a mop and mild cleanser or soap. And you have to dry it, because if water gets into it it'll rot. Also, they say you could apply a layer of Selbstglanzemulsion or Polymerdispersion. Do not use any kind of aggressive cleanser.

You can buy most basic cleaning supplies at Aldi/Lidl, but for a mop or something like that, try a drugstore (Schlecker, dm, Müller Drogerie, etc).

Firstly, have you been to a supermarket?

Why are you paranoid?

Damn, you are paranoid.

Learn the aspects of vinegar. 25% acidity is safe enough for someone like you to handle. Stay away from chemicals, you will blow your eye out.

Actually the U-Bahn cops in Munich are real, gun carring, dog handeling cops. They are a dept. of Stadt Polizei Muenchen. They have powers
of both the Tickets checkers (They stay on the Ubahn Network, while the BSG do the S-Bahns) and of Normal Cops. Best not to mess with them

Security guards are too a large extent overly agressive tossers with a complex that for the most part they were too thick to get into the Bavarian police!
Sadly they have Hausrecht in places like the U Bahn, S Bahn, beer tents at the Wies'n and the English Garden but not everywhere.

It's curiosity more than anything else (I don't live in the center of Munich so it's a bit weird seeing what appear to be security folk wandering around near the local shopping area) and I figured someone here may be able to clear it up.

I've seen another pair of them just now. Their logo thing contains four letters rather than three. Fairly sure it was ERHL. The full thing reads ERHL Security (with the security in English I guess as the German seems to be Sicherheit which it wasn't) Not sure if it was the same pair. I remember the dog last time being darker. This time it was a youngish Alsatian.

A shopping CENTRE might well employ such security guards as they have "Hausrecht" over their property but not on a public street.

EHRL is a whacking service: EHRL - Bewachungsdienst
They have the powers of X-Ray vision, mighty stength, the ones with the capes can fly, But they are not allowed to check tickets.

Incidently the U Bahn Wache has now been effectively privatised into a GMBH run by Securitas in which MVG retains a share.
The costs of the U bahn Wache come entirely from ticket sales apparently.

Munich City Council has thought about some kind of uniformed city police.
The lefties want it to be more of a tourist guide information warden, the CSU want them armed and to shoot anyone who "looks a bit foreign".

Thanks for that, Hardy's white wine all down my shirt now