"If I see (...) I will describe" translation to Latin

Question

Sentence to translate:

If I see dangerous ocean or beautiful mountains during my long journey I will describe them to you.

My attempt:

Si oceanum periculosus an montes pulchres in itinere meo longo videro tibi illos descripsero.

1. Are there any big mistakes (maybe a lot of them)?
2. Is an correct translation of or?
3. in itinere meo longo is all in ablative, it that correct?
4. videro and descripsero - I used future perfect here, to show that the seeing and describing should be completed.
5. illos in masculine perhaps because illos montes but maybe it should be illa?
6. Could you propose some better/correct translations?

Answer 1

1. There are a number of small mistakes. The biggest one in my opinion is the word an. Many will be covered by the subsequent points, but let me address the other ones here.

   The adjective periculosus should be in the same form as oceanum. It should be periculosum.

   The adjective pulcher should follow second declension (unless in feminine which is first declension), even though montes is third declension. The masculine plural accusative needed here is pulchros.

   However, pulcher is not the word I would choose here. It is a good choice for beauty in a human, but for beauty in nature I recommend amoenus instead. I would say that pulcher is more in the direction of "handsome" and amoenus is more like "picturesque", but I don't claim this is the whole story. Comparing these two adjectives (or other beauty adjectives) would make a nice and useful question.

2. The word an is a little difficult to describe. It is mainly used in questions (direct or indirect), often introducing the second option. See the linked dictionary entry for details. If you want to understand some aspects of this conjunction better, I recommend asking a separate question.

   The best "or" here is probably vel. See this question for a comparison of vel and aut.

3. Yes, it should all be in ablative. Similarly, if I want to say that I'm borrowing the horse of my good old rich Portuguese friend, then all those words (good, old, rich, Portuguese, friend) need to be in genitive.

4. If I have understood correctly, the difference between future and future perfect is not the same as the difference between imperfect and perfect. The future perfect is typically used for something that takes place before a future event. The main thing is that you will tell me something, and it will happen if you will have seen something. Therefore I would put the telling in the future tense (describam) and the seeing in the future perfect tense.

5. Here illos refers to both oceans and mountains. Since they both happen to be masculine, illos is the correct choice. See this question for details on choosing the gender of an adjective referring to several nouns — and note that ille is not an adjective. However, this particular case is simple since you refer to two masculines. Since the masculinity of oceans and mountains feels somewhat incidental and the things are inanimate, I wouldn't consider it a severe mistake to use neuter (illa) instead.

6. With the corrections proposed above, your translation is excellent. The word order and overall structure feel natural. Of course, there is room for variations. One possibility would be to use a chiastic word order: Si oceanum periculosum amoenosve montes in…