How to do large format printing?

Question

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Help me please. I read a lot about printing large format images. I'm confused. I don't want to end up digging in.
Friends had a board 6x3 meters. They asked to change the layout a bit. But they did not do it themselves, but advertisers. And they (acquaintances) threw off the layout in jpg, believing that this is the source. They don't have a vector, psd or tiff file.
Google gave me a lot of information. Now all this mess is in my head.
Please write point by point, or explain where I'm wrong:
1) What size canvas should be in Photoshop (for printing 6x3m)? From that porridge found in Google, I learned that the acceptable dpi for such printing is 30-45. I found a dpi converter and the resulting image. The size of the canvas is about 10k pixels by 5k pixels. Those. (correct me if wrong) then if I draw 2k by 1k pixels on a canvas with a dpi of 300, for example, and then increase it to 10x5, nothing will change much? But I don't know with what resolution the machines print.
2) Color profile? Clearly - CMYK. But what exactly? Photoshop has a bunch of them. At the moment I have selected - US Web Coated (SWOP) v2.
3) Is *.tiff being printed?
4) What else can I miss when preparing the layout?
Thanks in advance.

Answer 1

1.1. The scale is better than 1:1 or scaled, for example 1:10 (Depends on the printing house)
1.2. DPI is valid for such sizes and outdoor use 30-45, for interior - from 72 to 300
1.3. If you have a file with a resolution of 300 DPI and a size of 2000 x 1000 mm, if you drag the image into another document with a resolution of 35 DPI and a size of 10000 by 5000 mm, then nothing will change much, it will even be good. I recommend not to go crazy with converters, but to do it in Photoshop.
1.4. The resolution of the machine, oddly enough, depends on the machine itself =)
2. Color model - CMYK. US Web Coated (SWOP) v2 or Euroscale Coated V2 color profile (Printer dependent)
3.Basically, yes. It can also be PDF and Korel and Photoshop formats (Depends on the printing house).
4.1. Order a proof to "get in color"
4.2. Specify about the black color, more precisely its components (for example CMYK: 50/50/50/100), so that it does not turn gray
4.3. Together with the file, give a printout of the banner on an A4 sheet with the name of the file, what material to print on, and your contact details.
4.4. Well, to the heap next to the source, throw off a small jeep preview file for the convenience of printing.
4.5. The typography may have additional requirements, such as adding texture or noise to large solids. Also clarify.
Maybe post a preview, maybe I'll tell you what else is needed and what's wrong.
What he wrote "Depends on the printing house" - be sure to ask the printing house.