I wouldn't say that Wittgenstein is easy to read in any language haha. Why not read him in your native language for the ideas, and choose something expressing simpler concepts for practising English?

Don't read it. The first sentence is an improper compound sentence. Likely, the rest of the book is not well written either. 'The world is everything' is indeed a sentence but adding 'that is the case' without clarification or at least a conjunction makes it confusing and incomplete. While you say obscure words do not give writing it's depth and breadth, what is there to suggest an obscure word cannot give either, or both for that matter?

a) Do not get stuck with the very first proposition. Keep on reading. b) The Tractatus is certainly challenging to read but it's not poorly written. If reading philosophy is a foreign activity to you, you'd probably conclude this book is not well written. c) If you're interested in Wittgenstein's philosophy I would highly suggest to start with the Blue and Brown books and maybe move later to Philosophical Investigations.

The original German phrase: Die Welt ist alles, was der Fall ist. Considering the theme of Wittgenstein's book, this line may have been wordplay inspired by religious and metaphysical concepts around the word "fall". It probably doesn't simply mean "the case", although "case" is a similar-meaning multi-meaning word too (better suited to the back end of winter, while fall is the front-end of winter). "Der Fall" relates to the concept of what Americans call "Fall" and Brits call "Autumn" (the season of decline, when leaves are falling from trees, and daylight is decreasing). It also relates to the concept of the "fallen angels". It refers to everything heavy - every too dense to occupy the heavens. Physical matter, as opposed to energetic or celestial matter. Thus, all physical matter, and every thing that matters materialistically. Its opposite is spring - the springing back up - the ascension.