Learn French: Une vie minimaliste est très simple. - A minimalist life is very simple.

To use the restrictive negation ne... que (meaning "only" or "nothing but"), you place ne (or n') before the conjugated verb and que right before the word you are restricting. Here, it becomes: Une vie minimaliste n'est que simple.

Since vie is feminine, why don't the adjectives minimaliste and simple get an extra -e at the end?

In French, if the base masculine form of an adjective already ends in an unaccented -e, it doesn't change in the feminine. If we swapped the feminine noun une vie for a masculine one like un style (a style), the sentence would look exactly the same: Un style minimaliste est très simple.

Could I use beaucoup instead of très to say it is "very" simple?

No, this is a common mix-up! You must use très (very) when modifying adjectives (like simple) and adverbs. You use beaucoup (a lot / much) when modifying verbs (e.g., Il lit beaucoup) or nouns (beaucoup de choses).

Do I need to pronounce the -t in est and connect it to très?