There is a little coffee in the jar.

There is too much salt in the soup.

You eat too muchany biscuits.

There were too many that we had too leave.

Too many what?

He had too many cakes that, which made him sick.

How muchany concerts have you been to?

He spends too much time watching TV.

We had too msuch a good time together.

There is a little coffee in the jar.

“Little” by itself makes me think size of a solid object, but of course coffee doesn’t have a size in that same way.
“A little” or even “too little” would be a better fit.

There is too much salt in the soup.

When you say there’s an overly large amount of something, then you would say “too much” or “too many”.
“Too” by itself would be used in situations like “It’s too salty” or “the soup is too salty”.

You eat too muchany biscuits.

In this particular case it makes more sense if “biscuit” is plural, so “much” would change to “many”.
With biscuits, it doesn’t really make sense to say that you eat too much of one biscuit. My reasoning for it (but not necessarily the right reasoning) is that biscuits are quite small usually, and you don’t really save half of a biscuit for later like you might for chocolate or cheese.
If you had used this sentence with “chocolate” or “cheese” instead of “biscuit”, that would be right though. (As in “You eat too much chocolate” or “you eat too much cheese”)

There were too many (of what?) that we had too leave.

You should specify what there was too many of that you had to leave.

He had too many cakes and that made him sick.

Or “He had so many cakes that he felt/got sick.” In this sentence “felt” would be the better choice in my opinion though.

How muchany concerts have you been to?

Since you’re asking for a number (of concerts), concert should be plural (concertS). So then you would change much to many to agree with the plural word.
If you wanted concert to be a singular noun, the most similar sentence I can think of that makes sense would be “How much of a concert have you seen?”, which references one concert and asks how much the person has seen. (Answers to this question might be “I’ve seen half of a concert” or “I’ve seen a whole concert”). This would be a kind of unusual question to ask though.
“How many concerts have you been?” Would imply that the person the question is being asked to has been a concert (what I mean is that if you put “have you been” in the present tense, it would be “are you”, which basically implies that the person is a concert, or at least was in the past, and that of course isn’t right in any case).
Changing it to “how many concerts have you been to?” Is kind of like the equivalent of “how many concerts have you gone to?” Or “how many concerts have you attended?”

He spends too much time watching TV.

With “he”, spend —> spends

We had too msuch a good time together.

Or in the plural form - “We had such good times together.”
“Too much” isn’t really used with something positive like this, because it implies that you wish you hadn’t had so much of it. (I just thought of the saying “you can never have too much of a good thing” so that might be useful to remember this point).

We have mucha lot of time.

“Much” can be used, but “a lot of” would be better in this situation, and a lot of the time “a lot of” would be more common/natural too.

There is littlen't much coffee in the jar.

It would also be good to specify what form of coffee is in the jar. For example, is it brewed liquid or coffee beans? These sentences are disconnected but still the context has room for development.

There is too salt in the soup soup isn't salty enough.

Grammatically correct, however your original sentence doesn't sound that natural.

There were too many (people?), so we had to leave.¶
There were so many people that we had too leave.

In both correction scenarios, you'll want to specify the subject that is crowding you out.
"That" doesn't work unless you use "so" instead of "too" as outlined in the second potential correction.

He had too many cakes and that made him sick.

If consuming too many cakes made him sick, then not separating the sentence such as in this manner suggests that each cake individually was making this person sick.

How muchany concerts have you been to?

He spendt too much time watching TV.

Tense

We had too much of a good time together.

This sentence is still unnatural sounding. I'm unsure from context what you're trying to refer to exactly. How can you have too much of a fun time?

We have mucha lot of time.

There is very little coffee in the jar.

You could also say "There isn't much coffee in the jar."

There is too much salt in the soup.

You eat too muchany biscuits.

There were toso many that we had too leave.

He had too many cakes that made himand got sick.

you can also say: "He had so many cakes that he got sick."

How muchany concerts have you been to?

He spends too much time watching TV.

We had too muchany good times together.

We have mucha lot of time.

There is littlen't much coffee in the jar.

There is too much salt in the soup.

You eat too muchany biscuits.

Or, in the past tense, it would be "You ate too many biscuits".

There were too many thatpeople so we had too leave.

This sentence needs to specify too many of what- for example too many people, too much noise

He had too many cakes that made himso he felt sick.

or you could say "He had so many cakes that it made him sick."

How muchany concerts have you been?

When asking "how many" then use a plural noun- for example, how many apples, how many pages. "How much" is for money or for the quantity of one thing- for example "How much water have you drunk today?" "How much sun cream should I apply?"

He spends too much time watching TV.

We had too much good timefun together.

or "We had such a good time together"

We have mucha lot of time.

You can say "We don't have much time" but it's not usually used in the positive. You could also say "We have a long time until..."