Depuis hier, j’ai un rhume et mal à la gorge.

Because depuis means that something started in the past and is still true now.

So Depuis hier, j’ai un rhume means the cold started yesterday and you still have it.

This is a very common French pattern:

• J’habite ici depuis 2020. = I have lived here since 2020 / I’ve been living here since 2020
• J’ai mal à la gorge depuis hier. = I’ve had a sore throat since yesterday

A native English speaker may expect a perfect tense such as I’ve had, but French usually uses the present tense in this situation.

In French, the usual expression is avoir un rhume = literally to have a cold.

So:

• J’ai un rhume = I have a cold

You can also say:

• Je suis enrhumé if you are male
• Je suis enrhumée if you are female

That means I have a cold / I’m congested / I’m down with a cold.

Both are possible, but j’ai un rhume is very straightforward and common.

Because French, like English, often leaves out a repeated verb when it is understood.

So:

• J’ai un rhume et mal à la gorge
• J’ai un rhume et j’ai mal à la gorge

Both are correct.

The shorter version is natural because both parts go with j’ai:

• j’ai un rhume
• j’ai mal à la gorge

French often avoids repeating the same verb if the meaning is already clear.

Because avoir mal à + body part is the normal French pattern for saying that something hurts.

So:

• J’ai mal à la tête = I have a headache / My head hurts
• J’ai mal au dos = My back hurts
• J’ai mal à la gorge = I have a sore throat / My throat hurts

French usually expresses this idea with avoir mal à, not with an adjective the way English sometimes does.

Because the fixed expression is:

avoir mal à + body part

So the structure is:

• avoir mal à la gorge
• avoir mal au bras
• avoir mal aux jambes

The à is part of the expression. You do not normally replace it with de here.

French often uses the definite article with body parts where English uses a possessive adjective.

So French prefers:

• J’ai mal à la gorge
• Il a mal à la tête
• Elle s’est cassé le bras

English would usually say:

• My throat hurts
• He has a headache
• She broke her arm

This is a very common difference between French and English.

Because these are two different structures.

Un rhume is a noun phrase:

• un rhume = a cold

But avoir mal à la gorge is an idiomatic expression:

• mal here is part of avoir mal à, which means to have pain in / to hurt in

So the sentence combines:

• j’ai un rhume
• j’ai mal à la gorge

That is why the grammar is different in the two parts.

Because je becomes j’ before a vowel sound.

So:

• je ai is not used
• j’ai is correct

This is called elision.

You will see it often:

• j’aime
• j’habite
• j’écoute
• j’ai

It helps French sound smoother.

Yes. French often puts time expressions at the beginning, but other positions are possible.

For example:

• Depuis hier, j’ai un rhume et mal à la gorge.
• J’ai un rhume et mal à la gorge depuis hier.

Both are correct.

Putting Depuis hier at the beginning gives it a little more emphasis, as if you are setting the time frame first.

Normally, no. The natural expression is avoir un rhume.

So:

• J’ai un rhume = correct
• J’ai le rhume = usually not natural in standard French for this meaning

French treats rhume here as one instance of a cold, so it normally uses the indefinite article un.

A careful approximate pronunciation is:

duh-pwee yair, zhay uhn room ay mahl ah lah gorzh

A few useful points:

• j’ai sounds like zhay
• rhume has a French r, which is harder in the throat than in English
• et is pronounced like ay
• gorge sounds roughly like gorzh

Also, in natural speech, French is very smooth and linked together, so the sentence may sound more connected than an English speaker expects.