Dit bier smaakt verrassend goed.

Because bier is a het-word: het bier.

For singular nouns:

• dit is used with het-words
• deze is used with de-words

So:

• dit bier
• deze wijn
• deze auto

In the plural, Dutch always uses deze:

• deze bieren

Because dit already functions as the determiner. It works like English this in this beer.

So you say:

• dit bier not
• dit het bier

Just like in English, you would not say this the beer.

Smaakt is the third-person singular present tense of the verb smaken.

The subject is dit bier, which is singular, so the verb takes the singular form:

• ik smaak (rare in practice with this meaning)
• jij smaakt
• het/dit bier smaakt

The -t ending is the normal present-tense ending for most third-person singular verbs in Dutch.

Because Dutch makes a distinction similar to English:

• smaken = to taste, in the sense of have a certain taste
• proeven = to taste, in the sense of sample/try

So:

• Dit bier smaakt goed. = This beer tastes good.
• Ik proef het bier. = I taste / try the beer.

A good shortcut:

• if the food or drink is the subject, Dutch often uses smaken
• if the person is doing the tasting, Dutch often uses proeven

Here verrassend is being used adverbially. It modifies goed, not bier.

So the structure is basically:

• smaakt = tastes
• goed = good
• verrassend goed = surprisingly good

It is similar to English surprisingly in function, even though the Dutch form looks like an adjective.

Because it is not being used as an adjective before a noun.

Compare:

• een verrassend goed bier
  Here verrassend modifies goed → no -e
• een verrassende smaak
  Here verrassende modifies the noun smaak → it behaves like a regular adjective and gets -e

So in Dit bier smaakt verrassend goed, verrassend stays unchanged because it functions like an adverb.

Because goed is the word Dutch uses here for good/well in the sense of quality.

With verbs like smaken, Dutch normally says:

• Het smaakt goed.

Wel does not mean well in that sense.
Wel usually means things like:

• indeed
• actually
• yes, in contrast
• after all

So:

• Dit bier smaakt goed = correct
• Dit bier smaakt wel = incomplete or odd on its own

Yes, absolutely. That would sound very natural too.

There is a small nuance:

• goed = good, a bit more general
• lekker = tasty, delicious, pleasant to eat or drink

With food and drinks, lekker is often very common in everyday Dutch:

• Dit bier smaakt lekker.
• Deze soep is lekker.

So verrassend goed and verrassend lekker are both possible, but lekker focuses more directly on taste.

In a normal Dutch main clause, the conjugated verb usually comes in the second position. That is happening here:

• Dit bier = first element
• smaakt = conjugated verb in second position
• verrassend goed = the rest

So the sentence follows standard Dutch main-clause word order.

The phrase verrassend goed stays together because verrassend modifies goed.

Yes, but the basic sentence is the most neutral and natural one.

Neutral:

• Dit bier smaakt verrassend goed.

You can move things for emphasis, but then the sentence becomes more marked:

• Verrassend goed smaakt dit bier.
  This is possible, but it sounds literary or emphatic.

Dutch allows movement to the first position, but the verb still stays in second position, so the structure changes accordingly.

Not quite.

• Dit bier smaakt goed focuses specifically on taste
• Dit bier is goed is broader and could mean the beer is good in general: quality, brand, style, or overall opinion

So if you want to talk specifically about flavor, smaken is the better choice.