A lot of French fries. Colloquially "loads of French fries", "masses of French fries" "enough French fries to feed the Foreign Legion"... etc..... "sausage" is singular, "sausages" is the plural form. 1 sausage, 6 sausages

Many is correct, much is not. 'I shouldn't have bought so many french fries'. 'Why don't you give me some of your french fries, you have so many'

Most people would use "a lot" (slang) because it can be used without having to think whether the noun is countable or not. You can use the word, "plenty". "Too much French fries" is the correct way of saying. You can't count how many are there in the box at a glance. "Sausages" is countable. This is because ordinaryly, we are able to see how many there are on your plate at a glance. If you are talking about sausages on a serving plate, you use "There are many sausages". Now you will ask why "many" is used for sausages and "much" for French fries! So what's the difference between these two. This is because of the way they are being served. You are not served with one or two pieces of sausages while fries are served in a heap! Another example, "potatoes". There are many potatoes while there is much mashed potatoes! For example, most people call their countries "the motherland". However, you don't use it for Germany! It's the fatherland instead. This has to do with the custom of the natives. Learning English is difficult because of numerous exceptions.

you say a lot of french fries