A question about talking about things in general terms using German.
When you talk about things in general terms in German, do the nouns still need a marker?

Let me explain more what I mean with an example. I wanted to say "I think cake is very tasty", so I wrote "Ich denke Kuchen ist so sehr lecker". Two people have corrected the sentence to read "Ich denke, der Kuchen ist sehr lecker."

Forgetting the mistake of using so and sehr together, when I read "Ich denke, der Kuchen ist sehr lecker." to me, it says " I think the cake is very tasty". This is not what I was trying to say.

How do you talk about things in general terms in German? Do you still have to give the thing some kind of marker? Could you translate these few sentences to help me see more examples, please. Any of your own examples would be great also. Thank you!

1: I like dogs.
2: I think music is great.
3: Trees can be tall or short.
4: It is hard to write books.

Question

A question about talking about things in general terms using German.
When you talk about things in general terms in German, do the nouns still need a marker?

Let me explain more what I mean with an example. I wanted to say "I think cake is very tasty", so I wrote "Ich denke Kuchen ist so sehr lecker". Two people have corrected the sentence to read "Ich denke, der Kuchen ist sehr lecker."

Forgetting the mistake of using so and sehr together, when I read "Ich denke, der Kuchen ist sehr lecker." to me, it says " I think the cake is very tasty". This is not what I was trying to say.

How do you talk about things in general terms in German? Do you still have to give the thing some kind of marker? Could you translate these few sentences to help me see more examples, please. Any of your own examples would be great also. Thank you!

1: I like dogs.
2: I think music is great.
3: Trees can be tall or short.
4: It is hard to write books.

Answer

No, you don't have to use a marker. I assume the problem was the unusual sentence "Ich denke Kuchen ist sehr lecker". It's more natural to say: Ich mag Kuchen sehr or Ich finde Kuchen sehr lecker.

You would say what you said, if you have never eaten a cake and therefore don't know the taste.

Answer

I believe the correction goes more in the lines of subordinate clause (Nebensätze und Hauptsätze)

When you use denken (glauben, meinen etc...) you are creating 2 sentences the main sentence "Ich denke" and a subordinative clause "der Kuche ist sehr lecker".

You can tell that you have 2 verbs and two sentences hence the comma between them. Commas are very important in german language as they separate the main sentence from the subordinate clause. That's why people correct you the sentence to:

Ich denke,(comma) der Kuche ist sehr gut

Also that structre is only in spoken language, in text you would have to write:

Ich denke, dass der Kuchen sehr gut ist ( I think THAT the cake is very good)

Answer

The problem here is that the English sentence is not correct.
"I think cake is very tasty."
I can't get my head around this statement. My first response would be to ask what sort of cake is being talked about.

Anyway, to your other sentences:
1: I like dogs. = Ich mag Hünde
2: I think music is good for you. = Ich finde Musik sehr gut für die Seele.
3: Trees can be tall or short. = Bäume können hoch oder kurz sein.
4: It is hard to write books. = Est is schwer, Bücher zu schreiben.

In these instances it's the same as in English. Use the plural for countables and the singular for uncountables.

Answer

Why do you think that using so and sehr together is a mistake? I haven't seen it before, that's why I looked it in the Duden dictionary. It is not a mistake.