Links not working

I badly need this plugin to work because I have hundreds and hundreds of html pages and images to convert/import to wordpress and since I’m a complete beginner I can’t figure out any other way or implement any other solution to do that apart from this plugin.

My problems / questions:
1. I imported my html pages into my WordPress site, but the internal navigation links in the imported files don’t seem to work properly in the wordpress site. There are hundreds and hundreds of html pages and even more images – probably a few thousand elements in total. So, it’s not possible to fix manually! The problem specifically I noticed is that when I click, let’s say, the “Next” button in the menu of a page (converted into wordpress from my html) – it goes to a 404 page not found. What actually happens here is that the filename of the linked page is automatically appended at the end of the previous page’s URL along with that URL’s target file name instead of replacing that file name. But if I manually edit the URL of the linked page in the new browser tab’s address bar and remove the previous page’s filename from there, it then works. For example, here is a URL : https://example.sample.com/rockart/rockart-heritage-of-mars/part23/ . If I click “Next” in this page, it then leads to this: https://example.sample.com/rockart/rockart-heritage-of-mars/part23/part24.htm . “part24.htm” is simply appended at the end of the previous URL, instead of replacing the “part23” part of it. Instead of appending, if it replaced “part23” (without adding the “htm” extension), it would have worked, and it does if I do that manually in the address bar!! Apart from the starting page, all my pages are named serially like “part23.htm”, “part24.htm” etc. It also probably means (I haven’t checked thoroughly though) that all the pages uploaded and converted successfully, just not linked correctly any longer! Let me give another example. Take the same page mentioned above (part23) again and click on “Rockart” in the “Other sections” (navbar linking to other sections of the same subdomain staging site). This leads to another 404 with this URL: https://example.sample.com/rockart/Rockart/Rockart_Heritage_Of_Mars.html . You will notice a repetition of the word “rockart” in the URL. If you remove one of them (and the html at the end of the URL), then the real page will load. It’s right here: https://example.sample.com/rockart/Rockart_Heritage_Of_Mars . One final example. Here is an erroneous 404 URL: https://example.sample.com/rockart/marsculture_main.html . This is the homepage/entrypage/main ToCpage of this sub-site. I get this when I click “Main Contents” in the navigation section of other pages. The correct URL though is: https://example.sample.com/marsculture_main/ . There is no /rockart/ in the correct URL and shouldn’t be. I don’t know or understand why these things are happening.

2. My offiline html site (in my PC) with which I am experimenting the plugin after I uploaded my files to my subdomain’s wordpress ‘staging site’ – is structured like this:
Home (actually a Table of Contents/ToC page) linked to –> 9 separate ToC pages in 9 different folders on 9 different subjects –> The second-level ToC pages are then linked to the real pages of substance, images and CSS in their respective folders’ subfolders – 1 level beneath the 2ndary ToC pages mentioned. The pages inside the subfolders are linked to all the pages serially inside the same folder, to all the ToC pages mentioned above and also to ToC pages in other folders. That’s how the navigation works in the html site and that’s how I want it to be in the WordPress site too. One example from my offline site on my desktop: “marsculture_main.html/rockart/rockart_heritage_of_mars/part23.htm”. The first segment in this path is that of the main very first ToC page, the 2nd one is of the Subject folder or directory, the 3rd one is of the 2nd-level/subject-level ToC page, and finally the 4th one is of the actual content page inside a subfolder of its parent subject folder “rockart”. There is just one folder named “rockart” here. No other file or folder has the same name. Yet, it gets repeated in the erroneous URL mentioned above.

3. One last thing. I can see in the ‘pages’ section of my wordpress dashboard that all the header parts of my wordpress pages have turned into separate independent pages too additionally. Or most likely, these are the names of the folders (subject folders / directories mentioned above) turned into separate independent pages. I don’t really understand though why or how directory names can turn into pages. There are no html pages named like this.

4. As you can see, I am really a complete novice in website building. I don’t understand a lot of things yet. I am sure it’s not a fault or defect of the plugin. I must have made a mistake in configuring or using it – and can’t figure out what that is. So, can anybody please, please help me solve it?? I would be forever grateful and indebted to you!!!

Thanks in advance for all your help!