Let's start with a simple sentence.
It is hot.
If we want to strengthen it we can do the following:
It is very hot.
It is extremely hot.
It is really hot.
It is so hot.
It is such a hot day.
With the first four you add an 'adverb' before the 'adjective' to strengthen it. There are lots of synonyms for 'very' - you can use most.
The last one is slightly different in form, but not meaning.
Subject + verb + such (a) + adjective + noun
To use 'such (a)' you must add noun at the end. That noun is 'as what' you are describing the subject. Let's see some examples:
Books are such good presents.
'Books' are the subject here. They are being described as 'presents'. The adjective used to describe them is 'good'. There is no 'a' because the subject is being described as a plural thing (presents).
That is such a brilliant idea.
'That' is the subject (a previously mentioned idea). 'That' is being described as an 'idea' so 'idea' is at the end. The adjective being used is 'brilliant'. There is an 'a' because the subject is being described as a singular (idea (one)).
I had such a good time last night.
The subject is 'I'. You are describing 'time' (as in what you experienced) and it is described as 'good'. 'Last night' is a time adverbial and is there to make it sound natural.
How about a negative example. We can do it two ways.
I didn't have such a good time last night.
I had such a terrible time last night.
Books aren't such great presents.
Books are such rubbish presents.
Change the verb negative
Change the adjective to it's antonym.
Can we use 'such (a)' with questions? Absolutely.
Is that such a good idea?
Are books such good presents?
Is it such a hot day?
NOTE: You would not start the conversation with a question using 'such (a)'.
Conversation:
A: I'm going to buy mum a book for her birthday.
B: Really? Are books such good presents?
A: Yeah, everyone loves books.
B: Not me. I've got so many I haven't read.
A: It's so hot!
B: It's hot here too.
A: How hot is it there?
B: 23 degrees.
A: Is it such a hot day?
B: For me, yes.
Conclusion
Such (a) = very
Needs a noun after the adjective
Two ways to make negative
Can't start conversations using it
Give me your examples below and remember:
Subject + verb + such (a) + adjective + noun