Your recent post on this topic was answered - and resources were provided that attempted to provide comprehensive explanation of iPadOS Safari’s advanced features and functionality.
Please remember, we’re all end users, just like you. Where possible, the majority of volunteers here make genuine attempts to assist others with their difficulties. I recall that your previous response to help and suggestions, in context of this issue, was less than “enthusiastic” towards the community contributors that were genuinely trying to provide practical help.
I certainly recognise that a misplaced or accidental “tap” within the iPadOS dynamic action menus can have unexpected consequences - some of which, for Safari, can result in apparently lost tabs or windows. Many of these situations are recoverable - others less so.
When understood, the advanced features of iPadOS Safari work very well and consistently. The Split Screen and Slide-over views are useful in many cases, in particular when working between two different Apps. For example, when drafting a document, you might need to look-up a web-resource - or perhaps need to quickly access a Note or other document.
Larger screen devices can simultaneously display a Split-screen (two instances of a one App - or two different Apps) and a Slide-over view of a third App/instance. This windowing capability may not be needed by many iPad users, but these functions are useful for some.
With the release of iPadOS13, Apple introduced additional functionality that exploits the capabilities of larger screen devices, accommodating those users with more advanced needs.
For those users who prefer the simpler functionality of earlier iOS versions for iPad, multi-tasking features of iPadOS can be easily disabled:
Settings > Home Screen & Dock > Multitasking > Allow multiple Apps - set to OFF
Disabling multitasking won’t resolve difficulties associated with a misplaced “tap” in an action menu, but does remove the UI-complexities associated with multiple App instances and Safari “spaces” (windows).
Your description of immediate difficulties might suggest that you are perhaps having problems with managing multiple Safari Windows. As such, I believe that your immediate problem would be best addressed by disabling multitasking on your iPad.
I sincerely hope this advice proves to be helpful to you.