At the end of the second paragraph, you're missing a space between "not" & "simply".

In you third paragraph, you used the singular "tends" instead of the plural "tend". In addition, though I believe the sentence to be grammatically correct even without them, adding commas before & after "as in principle" would make the sentence a bit clearer.

Finally, your last paragraph. The second sentence is quite long, it would be more readable if you added commas before the "and" & after the second "it's". A comma could be placed just after "Often", but the sentence remains legible even without it. The sentence could use quotation marks to improve readability further, which would end the sentence on a question mark followed by an ending quote. This would be grammatically correct in American English, but as the sentence is not a question, a period should be added to the end. While it may have been intentional, for comedic effect, "biq" should be "big" & "mystake", "mistake". If I've understood the sentence correctly, the newly-corrected "mistake" should be in its plural form, "mistakes", and be followed by a comma. The sentence should also end with a period.