يهنئ صديقي العريس ويلقي نخبا.

Because this is a normal verbal sentence in Arabic. A very common word order is:

verb + subject + object

So:

يهنئ صديقي العريس
= congratulates my friend the groom

In natural English, of course, we say My friend congratulates the groom.

Arabic could also say:

صديقي يهنئ العريس

but starting with the verb is very common in Modern Standard Arabic.

صديقي means my friend.

It breaks down like this:

• صديق = friend
• -ي = my

So صديقي literally means friend of mine / my friend.

This is a very common Arabic pattern:

• كتابي = my book
• بيتي = my house
• صديقي = my friend

It is the person doing the action of يهنئ and also of يلقي.

In يهنئ صديقي العريس:

• يهنئ = he congratulates
• صديقي = my friend → the doer, so it is the subject
• العريس = the groom → the person receiving the action, so it is the object

A learner may expect the subject to have a clear visible nominative ending, but with صديقي, the ending is not obvious because of the attached -ي (my). So you identify it mostly by grammar and meaning.

Because العريس is the one being congratulated.

The verb يهنئ takes a direct object, and here that object is العريس.

With full vowels, it would be:

العريسَ

The fatḥa shows the accusative, which is the normal case for a direct object in MSA.

So:

• صديقي = the one who congratulates
• العريسَ = the one being congratulated

يهنئ is the present tense verb meaning he congratulates.

Its dictionary form is:

هنّأ = to congratulate

So:

• هنّأ = he congratulated
• يهنئ = he congratulates / he is congratulating

It is pronounced roughly:

yuhanniʾu

Two details often matter to learners:

• the shadda on ن means that sound is doubled
• the final hamza is real and should be pronounced as a glottal stop

So it is not just yuhanni; the hamza at the end still matters.

و means and, and يلقي means he delivers / he gives / he casts, depending on context.

So:

ويلقي = and he delivers / and he gives

Here it is connected to the first verb:

• يهنئ = he congratulates
• ويلقي = and he delivers

The subject is still صديقي.

So Arabic does not need to repeat the subject:

• يهنئ صديقي العريس ويلقي نخبا
• literally: My friend congratulates the groom and delivers a toast

No. They are completely different.

In صديقي, the -ي means my.

But in يلقي, the final ي is just part of the verb itself. It does not mean my.

So:

• صديقي = my friend
• يلقي = he delivers / gives, with no possessive meaning in the final ي

This is a very common thing learners need to watch for: not every final ي is a suffix meaning my.

Because Arabic can simply move to a second verb and leave the subject understood.

So in:

يهنئ صديقي العريس ويلقي نخبا

the second verb يلقي already contains he, and that he naturally refers back to صديقي.

English often works similarly:

• My friend congratulates the groom and gives a toast.

We do not usually repeat my friend before gives either.

This is the normal spelling of many indefinite accusative nouns in Arabic.

The ending ـًا is tanwīn fatḥ. It is often written with an extra alif.

So نخبًا is written with:

• the final fatḥatayn
• and a written alif

This does not mean there is a separate extra word or suffix there. It is mainly an orthographic pattern showing the -an ending.

In this sentence, نخبًا is the object of يلقي, so the accusative makes sense grammatically.

Its basic meaning is and.

In many contexts, و simply joins two actions:

• he congratulates
• and he gives a toast

Depending on the context, English might sometimes express that more smoothly as while or as, but grammatically the Arabic و here is just the normal conjunction and.

So the safest understanding is:

My friend congratulates the groom and gives a toast.