Der Teig bleibt zu flüssig, deshalb gebe ich mehr Mehl hinein.

Because Teig is the subject of the first clause, so it is in the nominative case.

• der Teig = the dough (subject)
• den Teig = the dough (direct object)

In Der Teig bleibt zu flüssig, the dough is the thing that remains/stays too runny, so it has to be nominative.

Bleibt is the 3rd person singular form of bleiben, which means to stay or to remain.

So:

• Der Teig bleibt zu flüssig = The dough remains too runny

German often uses bleiben in situations where English might also say is still:

• Der Teig bleibt zu flüssig = The dough is still too runny / remains too runny

Since Teig is singular, the verb is bleibt.

Zu + adjective means too + adjective.

So:

• flüssig = liquid / runny
• zu flüssig = too liquid / too runny

With dough or batter, English would usually say too runny or too liquid depending on context. The grammar point is that zu is the normal word for too before an adjective:

• zu kalt = too cold
• zu teuer = too expensive
• zu schnell = too fast

Because this sentence contains two main clauses:

1. Der Teig bleibt zu flüssig
2. deshalb gebe ich mehr Mehl hinein

In German, when two main clauses are joined like this, they are often separated by a comma.

Here deshalb means therefore / that’s why / for that reason, and it introduces the second main clause.

Because deshalb takes the first position in the second main clause, and in a German main clause the finite verb must come in second position.

So the structure is:

• deshalb = position 1
• gebe = position 2
• ich = then comes the subject

That is why you get:

• Deshalb gebe ich mehr Mehl hinein.

This is a very common pattern in German:

• Ich bin müde, deshalb gehe ich ins Bett.
• Es regnet, deshalb bleiben wir zu Hause.

Even though ich is the subject, it does not have to come first in German main clauses.

German word order is based on the verb-second rule in main clauses, not on subject-first order.

In English, the subject usually comes before the verb:

• therefore I add

In German, the verb must be in the second position:

• deshalb gebe ich

If the sentence started with ich, then you would say:

• Ich gebe deshalb mehr Mehl hinein.

Both are possible, but they emphasize the sentence a little differently.

Because Mehl is being used here as an uncountable material noun, like flour in English.

So German normally says:

• mehr Mehl = more flour

not usually:

• ein mehr Mehl ❌

This is similar to English:

• more flour
• more water
• more sugar

Also, mehr here means more, not several or many.

Mehl is in the accusative case because it is the direct object of gebe.

• ich gebe mehr Mehl hinein = I add/put in more flour

However, with Mehl, the nominative and accusative forms look the same:

• nominative: das Mehl
• accusative: das Mehl

So you do not see a form change here. If it were a masculine noun, the article would change more clearly.

Hinein means in / into it / inside, with a sense of movement inward.

In this sentence:

• mehr Mehl hinein geben = to add/put more flour in

It helps express the idea of putting something into the mixture.

A useful distinction is:

• hinein = into the inside, often with a sense of direction
• herein = in here / into here, toward the speaker
• rein = a common shorter form of hinein in everyday speech

So you may also hear:

• Ich gebe mehr Mehl rein.

That is more colloquial.

In this sentence, it is best understood as geben ... hinein, where hinein functions like a separable directional element.

That is why it appears at the end:

• Ich gebe mehr Mehl hinein.

This is very common in German with verbs of motion or placement:

• Ich stelle die Milch hinein.
• Sie wirft das Papier hinein.

In everyday learning, it is useful to remember the pattern:

• verb in second position
• directional particle at the end

Yes. That is also correct.

Compare:

• Der Teig bleibt zu flüssig, deshalb gebe ich mehr Mehl hinein.
• Ich gebe deshalb mehr Mehl hinein.

The difference is mainly word order and emphasis:

• deshalb gebe ich ... puts deshalb first, strongly linking the action to the reason
• ich gebe deshalb ... starts with ich, which is a little more neutral or speaker-focused

Both are grammatical.

Yes, in many contexts they mean almost the same thing: therefore / that’s why / for that reason.

So you could also say:

• Der Teig bleibt zu flüssig, deswegen gebe ich mehr Mehl hinein.

Both are very common. Deshalb can sound slightly more formal or written in some contexts, but both are standard everyday German.

Yes, flüssig literally means liquid, but it is also commonly used more loosely for mixtures that are too thin, too runny, or not thick enough.

So with cooking or baking, zu flüssig often means:

• too runny
• too thin
• too watery/liquid

The exact English wording depends on the context, but the German is completely natural.

The original sentence is already natural. But in everyday speech, people might say things like:

• Der Teig ist noch zu flüssig, deshalb gebe ich noch mehr Mehl rein.
• Der Teig ist zu flüssig, also gebe ich mehr Mehl dazu.

Some differences:

• ist noch zu flüssig = is still too runny
• rein instead of hinein = more colloquial
• also instead of deshalb = very common in speech
• dazu can also be used in cooking contexts for to it / in addition

So your original sentence is correct and natural, just a bit neat and standard.