In addition to whichever dictionary and textbook you use, as you get deeper in, an Allen & Greenough grammar reference is really handy. Because Latin word-order is looser than English, there are some a-ha! moments where it starts to click, "Oh, this entire clause is acting as the direct object, and it's here because Cicero wanted to emphasize this and this." Quickly being able to look up common constructions and how noun cases are used helps with that.
The word ordering stuff gets really wild, compared to my native English. I wonder about languages that have more flexible word order, do their speakers have greater ability to retain information in working memory?
keep in mind that most of the latin you end up reading in school is rather formal/complex. it's hard to parse in a similar way that charles dickens is harder to parse than casual/informal english. stuff like de bello gallico and some new testament books (greek) can be very straightforward.
it is definitely hard to get started with latin/greek when your native tongue is a highly positional language like english, but I don't think it is intrinsically harder. the same information is there, it's just encoded in word endings rather than order. in english, the word order is only really important within individual clauses. you can still write very complicated (and syntactically correct) english sentences with clause orderings that are very hard to parse. I'd argue this requires just as deep of a mental "stack" as latin/greek.
anyways, that's just my two cents as someone who studied, but never fully mastered, latin and greek in college.
