How to browse through the Wiki?

Is there a TABLE OF CONTENT page,showing a structure of the Wiki? That would make the bowsing easier.

Not exactly, because the wiki constantly changes so the people would spend a lot of time updating a ToC. I think the Main page shows useful links and you can click them to dive into a topic as in a hierarchical overview.

If not, what advice would yuo give somebody like me, in order to find my way around?

I would read Searching the wiki to understand how the search works and have a look at the Page naming convention. The latter is useful when judging search suggestions like the difference between the wiki pages "Railways", "Key:railway", and "Sweden/Railways".

You mean something like https://wiki.openstreetmap.org/wiki/Contribute_map_data? (I suppose https://wiki.openstreetmap.org/wiki/Category:Portals have long been forgotten in the age of search engines)

Should be easier to look for what you need as you go and encounter problems in editing culminatively. No need to get Wikipedia Syndrome (it's easier to fall into "just one more change" edits).

If wiki searching fails you (DuckDuckGo has a !osmw bang), use site:https://wiki.openstreetmap.org or similar on your search engine.

The Map Features page can be seen as a TOC of the documentation of tagging practices.

With it being a wiki, anyone can create a page so the structure can best be described as 'loose', a regrettably for the newbie, quite a few of the pages appear to have been written with the purpose of showing off how much detail the writer knows about a subject, rather than make it clear for a contributor just starting out.

As with many organisation's websites I've found Google's site search option more productive than the built in one. This way you'll come across a few isolated pages which aren't linked.

I wouldn't take what's in the wiki as gospel. it can often be at odds with what's used in the database. If you want to see if a certain tag is popular use this site: https://taginfo.openstreetmap.org/ And if you wish to discuss any queries there's this site, or the tagging forum: https://lists.openstreetmap.org/pipermail/tagging/

Hi you could search line in your PC for anything in the OSM wiki at anytime. For instance 'OSM Wiki oil" and the result is as follows Tag:industrial=oil - OpenStreetMap Wiki https://wiki.openstreetmap.org/wiki/Tag:industrial%3Doil 11 Jun 2020 ... Description. Oil industry - includes the global processes of exploration, extraction, refining, and marketing petroleum products. Edit or translate ... and several more cataegories containing the key word oil.