طعم هالسلطة منيح، بس بدي شوية ملح.

In Levantine, this is often expressed as a noun phrase rather than a verb phrase.

Literally, طعم هالسلطة منيح is:

• طعم = taste
• هالسلطة = this salad
• منيح = good

So the literal structure is The taste of this salad is good.
Natural English usually turns that into This salad tastes good.

Yes. In present-tense sentences, Levantine Arabic usually leaves out the verb to be.

So:

• طعم هالسلطة منيح = The taste of this salad is good

There is no spoken word for is here. That is completely normal in Arabic.

هالـ is a very common Levantine way to say this before a noun.

So:

• هالسلطة = this salad
• هالبيت = this house
• هالبنت = this girl

In colloquial writing, it is often written attached to the noun, which is why you see هالسلطة as one word.

Because منيح describes طعم and not سلطة.

• طعم = taste, and it is masculine
• سلطة = salad, and it is feminine

So the sentence means The taste of this salad is good, and good must agree with طعم, not with سلطة.

Compare:

• طعم هالسلطة منيح = The taste of this salad is good
• هالسلطة منيحة = This salad is good

In the second sentence, منيحة is feminine because it describes السلطة.

Here, بس means but.

So:

• طعم هالسلطة منيح، بس بدي شوية ملح = The salad tastes good, but I want a little salt

But بس can also mean only or just in other contexts.
So its exact meaning depends on where it appears in the sentence.

بدي is the common Levantine way to say I want.

It is extremely common in everyday speech.

Some related forms are:

• بدي = I want
• بدك = you want
• بده = he wants
• بدها = she wants
• بدنا = we want

This is colloquial Levantine, not Modern Standard Arabic. In MSA, a learner may know أريد, but in daily Levantine, بدي is much more natural.

شوية means a little, some, or a bit.

In this sentence:

• شوية ملح = a little salt / some salt

Because salt is an uncountable noun, English may translate it as either a little salt or some salt.

Because after a quantity word like شوية, Arabic normally uses an indefinite noun.

So:

• شوية ملح = a little salt
• شوية سكر = a little sugar
• شوية مي = a little water

The idea is not the salt in particular, but simply some salt.

They are very close in meaning, and both can mean this salad.

But هالـ is especially common directly before nouns in Levantine:

• هالسلطة = this salad

هاي is also a demonstrative, and in some dialects you may hear:

• هاي السلطة

Both are understandable, but هالسلطة is a very natural everyday Levantine form.

Yes. A few common alternatives are:

• هالسلطة منيحة، بس بدها شوية ملح
  = This salad is good, but it needs a little salt

• طعمها منيح، بس بدها شوية ملح
  = Its taste is good, but it needs a little salt

So the original sentence is natural, but there are several everyday ways to express the same idea.