Lucky for you, I am an expert in these things.
Each type of document should be treated differently.
I recommend making a copies of all of these items in case they get lost or are damaged in the process. Copying may damage them slightly, but it will also ensure you have an extra, newer copy for the future. At the very least, make an index of the type of documents that you have and keep it seperate from the documents (ie- make a list of the documents & their contents on your computer). With pictures, identify as many people/places as possible and write them on the seperate piece of paper.
Technically, they recommend wearing gloves while handling documents you want to preserve, but this isn't always practical. Handle the documents as little as possible. If you do handle them, make sure that your hands are clean and only hold them by the edges. Acid & oils from your fingers will degrade photos over time.
Store your documents in a cool, DRY & dark environment. Use only archival quality envelopes or boxes to store the items in. The US Library of Congress likes to use uncoated archival quality polyester film (a transparent film protective covering). Do not write on the back of the photos. Do not take photos out of an album.
I'm not sure about Slovenia, but here in the United States, libraries and museums are excited to receive treasure-troves of information as a donation to their collection, especially if they are unique or in incredible condition. They also know how to best preserve your documents and what value they have. Very often if documents are well-preserved, the very place they were found is the best place for them. This, too, isn't always practical since they might be things you would like to look at frequently, display, show-off, share, etc.
There are many companies that specialize in preservation, some for free, most for profit that can help you better meet the more specific needs of your documents.
Best of luck!