And there are some adjectives which change meaning depending on whether they are after or before the noun. However, I have noticed that when these adjectives change meaning, often it the meaning that it has when before the noun has some degree of emotion or personality to it.
For example, ma propre chemise vs ma chemise propre (my own shirt vs my clean shirt). Or mon cher ami vs ma chère chemise (my dear friend vs my expensive shirt).
So in my experience, that was not the hard part of learning French, or Spanish for that matter. For someone coming from a non-gendered language, the gender of nouns is taxing to memorize. Often knowing what the correct word is and how it is spelled will have nothing to do with what gender it is.
The other hard part of learning French (for me) was the conjugation of verbs in various tenses, and specifically any words that are exceptions to the normal rules. If you take a look at a french grammar book for (e.g.) English speakers, it's likely that it will mostly concern conjugation.
For example, ma propre chemise vs ma chemise propre (my own shirt vs my clean shirt). Or mon cher ami vs ma chère chemise (my dear friend vs my expensive shirt).