Hi! I need some advice on two projects I am working on. One is a logo design that I made too big ( I think) and the other is a photo I will be editing which I will need in different sizes for different formats.

1. Logo:

I scanned a drawing and traced it with the Brush tool. I resized it, assuming that bigger is better, and worked on a 5000x3500 px canvas. I think I need it smaller though, to insert it in a header but also use it as small logo on a flyer for example. This image will also be used as a facebook profile picture etc.
For the header, the webdesigner said it should be about 350 px high... When I resize the image using the Box filter to 350 height, it gets really pixelly and bad.
Can someone help me out?
- how can I resize the image (make it smaller) and still retain image quality?
- do I even need to resize it ? if I upload it with its current size will it be okay?


2. Illustration for several formats

I am also working on an illustration that will be used for several different purposes: background for a flyer (that will be printed, A6, possibly A7) but also a website image (and soundcloud image).
To avoid resizing issues, what canvas size should I work with?
Some info on the design: I will be modifying a photograph collage-style


I hope this is clear enough! I would be very grateful for some input, I'm very self-taught and need help especially with the technical side of things.
Thank you!

My take on this is that you shouldn't resize your working canvas, work on it as big as you need/can, and only then export to a png/tiff, then use that image (not the kra.) to resize it to the desired size, (just remember to keep proportions). I haven't use Krita for pure resizing (I'm used to Gimp for photo manipulation) but I'm thinking shouldn't be any problem, also, logos are much better done in vector graphics, those scale without pixels.

I'm sure there are much better/detailed answers, but for starters there you go