Clarifications on the use of "depuis" with the "passé composé"

Question

I have been revising preposition "depuis" and its uses in a sentence.

I understand that "depuis" is used to talk about an action that started in the past and that is still true/ongoing in the present (what in my days used to be called "duration form"). It is often used with the present (because the action/state is still happening).

However, we also know that "depuis" can be spotted in sentences where the "passé composé" is used, especially with:

a) passé composé à la forme négative, e.g. Je n'ai pas bu depuis deux jours

b) passé composé "durable", which according to the book Grammaire Progressive du Français, are verbs containing an idea of movement (sortir, rentrer), evolution (s'améliorer, se stabiiliser), beginning/end (arrêter, commencer, etc.) and change of state (maigrir, grossir, augmenter, etc.)

E.g. David a disparu depuis quatre mois

I have a few questions around points a) and b) above.

1) When we use the passé composé in the negative form, am I right to say that we can generally use the present tense in the negative form as well?

E.g., je n'ai pas bu depuis deux jours = je ne bois pas depuis deux jours
je ne l'ai pas vue depuis trois semaines = je ne la vois pas depuis trois semaines.

If the answer is no, could someone please explain when you would use the passé composé and when the present in this case?

2) In the two sentences above from 1), "depuis" cannot be replaced by "il y a", is that correct?

3) For the verbs expressing this concept of "passé durable" (which I am not sure I have fully grasped - my research online did not lead to much, but I think it is a past where we are interested to show the results of the action on the present/the permanence of its effects on the present), can I just check that the following sentences are correct? I just want to put the theory to the test with native speakers to check that the rule is actually 100% accurate.

a) J'ai abandonné mon rêve de devenir pilote depuis dix ans

b) Elle est morte depuis quatre jours

c) Sa santé s'est améliorée depuis le retour de son mari

d) J'ai commencé à conduire depuis l'âge de dix-neuf ans

e) Il est allé au supermarché depuis ce matin

Thank you very much for any help you will be able to give me.

Answer 1

1) When we use the passé composé in the negative form, am I right to say that we can generally use the present tense in the negative form as well?

The examples you give do not really sound very good in French. I'll compare to how you'd translate them in English:

"je ne bois pas depuis deux jours" literally translates to "I don't drink since two days", which doesn't sound pretty good. "je ne la vois pas depuis trois semaines" has the same issue.

This is where the word "plus" enters and associates with the negative form. It is used in French to refer to something that happened before but doesn't anymore. For instance,

Je ne lis pas de BD / I don't read comics

and

Je ne lis plus de BS / I don't read comics anymore

So if you want to use the present tense in these sentences, you have to indicate the fact that the action isn't happening anymore.

"je ne bois pas depuis deux jours" becomes "je ne bois plus depuis deux jours", which means "I haven't drunk in two days" and indicates that you're not planning to go back to drinking any time soon.

In the same fashion, "je ne la vois pas depuis trois semaines" becomes "je ne la vois plus depuis trois semaines", which indicates that you haven't seen her in three weeks and implies that you're not willing to in the near future.

2) In the two sentences above from 1), "depuis" cannot be replaced by "il y a", is that correct?

I'd say so, yes. Depuis could translate to since and il y a is closer in meaning to ago.

If you say "je n'ai pas bu il y a deux jours", it means you haven't drunk anything two days ago. It doesn't necessarily say anything about your consumption for the following days. This sentence translates to "I didn't drink anything two days ago", which as you can see is different from "I haven't drunk anything in two days".
One can say "il y a X [temps]" refers to something that happened in the past and has stopped since.

3) [...] can I just check that the following sentences are correct?

"J'ai abandonné mon rêve de devenir pilote depuis dix ans" doesn't sound very good because it means you have been giving up on your dream every day for the last ten years. Giving up on something isn't something that lasts in time, it's a finite action. It should rather be "J'ai abandonné mon rêve de devenir pilote il y a dix ans".

"Elle est morte depuis quatre jours" -> "She died for four days". Same problem here, dying is a finite action in time, il y a makes more sense in this context. "Elle est morte il y a quatre jours".

"Sa santé s'est améliorée depuis le retour de son mari" this one is good. Recovery is a gradual process, so it's no surprise that their health has gotten better and better ever since their husband returned. You don't get better on the spot.

"J'ai commencé à conduire depuis l'âge de dix-neuf ans": in this sentence you mention both the beginning of an activity (so something that is finite and happened once) and a duration (since the age of 19, but you haven't been beginning to drive every day since that age).

Depending on what you're trying to express this sentence could either be corrected to

"J'ai commencé à conduire à l'âge de 19 ans" ("I began driving at age 19")

or

"Je conduis depuis que j'ai 19 ans / depuis l'âge de 19 ans" ("I've been driving since I was 19 / since age 19")

"Il est allé au supermarché depuis ce matin": This one has the same problem as before. If you want to focus on the fact that he went to the supermarket (which is a finite action), you'd say "Il est allé au supermarché ce matin" ("He went to the supermarket this morning"). However, if you want to focus on where he's been this whole time, you would say "Il est au supermarché depuis ce matin" ("He's been at the supermarket this morning/all morning long").