Can I use much in a positive sentence?

It sounds formal or odd in speech. Use a lot of instead: We have a lot of work.

What is the difference between a few and few?

A few means some, which is positive. Few means almost none, which is negative.

Grammar, compared

Many goes with things you can count. Much goes with things you cannot. A lot of works with both.

Countable / Uncountable
Countable	Uncountable
How many students are there?	How much time do we have?
There are a few chairs. (Enough.)	There is a little milk. (Some.)
There are few chairs. (Not enough.)	There is little milk. (Almost none.)

Quantity words compared
Word	Goes with	Example
many	Countable plural, in questions and negatives	How many friends do you have?
much	Uncountable, in questions and negatives	I don't have much time.
a lot of	Both, in positive sentences	I have a lot of friends. A lot of money.
a few	Countable plural, some	A few days ago.
a little	Uncountable, some	A little sugar, please.
few, little	Almost none, a negative idea	Few people came. There is little hope.

Mucho covers both in Spanish: mucha gente, mucho tiempo. In English choose: many people, much time.
In positive sentences, say a lot of: I have a lot of friends, not I have much friends.
Information, advice, news, furniture, homework, luggage, money and traffic are uncountable. Say some information, a piece of advice.
A few and a little sound positive. Few and little sound negative: I have a few friends (good) or I have few friends (sad).

Can I use much in a positive sentence?: It sounds formal or odd in speech. Use a lot of instead: We have a lot of work.
What is the difference between a few and few?: A few means some, which is positive. Few means almost none, which is negative.

Book a trial class. She writes back with times in Buenos Aires time.