Each language has its tricky points, and Spanish isn’t the exception. While the easy spelling and fairly straightforward pronunciation are great, you will come across some struggles that take some time to overcome when you’re learning how to speak Spanish and also when you are writing in Spanish. Among the most difficult points are:
Ser and Estar: These are two verbs that make up one in English: to be. Ser is used for permanent situations of “to be.” Estar is used for temporary situations of “to be.” It takes a while to sort out when to use each one, because in English you never make that choice. As they say, practice makes perfect, and taking the time to study the lists of examples of when to use each one eventually pays off. Lots of fill in the blank exercises are useful as well because they force you to choose between the two options, giving you the chance to practice and memorize those lists you studied. Here you have a longer explanation about SER and ESTAR.
The subjunctive: Another part of Spanish that doesn’t really quite exist in English, or at least is rarely used, is the subjunctive. It’s difficult for those who want to learn to speak Spanish to use the subjunctive correctly. Even advanced students struggle with it. The subjunctive tense, sometimes described as a mood, is used when uncertainty is expressed. For example, “I doubt he’ll go” in Spanish would use the subjunctive “vaya”, making the sentence “Dudo que vaya” rather than the indicative and incorrectly stated “Dudo que va.” To further complicate the subjunctive, it can be used with all verb tenses and also in adverbial clauses, adjectival clauses, to make requests and in various other instances. When asking native speakers how they know when to use the subjunctive, you’ll likely hear a very unhelpful answer: “it just sounds right.” Well, that just means you’ve got a lot of listening and speaking practice to do.
All those tricky phrases and expressions: Once you’ve got down the basics of Spanish, you’ll start to realize that there are many fluffy, formal phrases used for certain situations and topics. While English tends to be very direct and to the point, Spanish tends to be more flowery and nuanced. There are certain phrases that if translated literally don’t seem to make much sense, but are used in certain situations. For example, to thank someone for an email or letter, it’s normal to write “Tengo el gusto de acusar recibo de su carta” (I am happy to acknowledge receipt of your letter). At a funeral or when someone has died, you should say “Mi más sentido pésame” which is the equivalent of “I’m sorry for your loss”. These are the sorts of phrases you wouldn’t come up with on your own even if you have a fairly large vocabulary. Then of course, there are many more idiomatic expressions and slang that you’ll encounter and once you start interacting regularly in Spanish you’ll have to learn them. You’ll have to work hard to keep up with conversations between native speakers and ask when you don’t understand. Get started by learning some of these expressions.