"that much" cannot be used to modify adjectives unless they are comparative adjectives s.a. alike; different. "that much" is usually used to modify comparatives s.a. higher, taller, shorter; more crazy etc. or mass noun s.a. water; food; trash etc.
That much high (❌)
That much higher (✔)
That much high level (✔) => 'high' modifies 'level' and 'that much' modifies the phrasal noun 'high level'.
그 + Noun-은/는 = The aforementioned N / That N, where 그, "That" is a "referential The" (abstract, not in sight object)
그 + Noun-이/가 = The N indicated/ That N (there), where 그, "That" is a "indicative/identificative The" (concrete, pointed-out object)
This is why sometimes 그, is seen translated to "The" (an emphatic "The").
--> 그, used to refer to thing(s) physically close to the listener or to refer to some abstract (not in sight) matters (things or concepts) known to both interlocutors.
--> 저, used to refer to thing(s) physically at some distance away from the interlocutors. 저 always refers to things "visible" to the interlocutors.
"The" as definite article is never translated into Korean. For emphasis as in "The ... there", use "That". (* In English, "that" is known as the "emphatic the".)
The word 는 is one of the particles used in Korean. Along with 이/가, 은/는 are used to specify the subject of the sentence. But the difference is that 은/는 are more general and 이/가 are emphasizers. So, lets take an example - 여자가 would mean 'The woman' while 여자는 would mean 'A woman' And also if you're confused about the usage of 이/가 and 은/는, 이 and 은 are used with words ending in a vowel and 가 and 는 are used with words ending in a consonant :)
(1) 크다 = be big/large [size]
키가 크다 = tall [height]
높다 = high [height]
▪키가 크다 (tall) usually applies to people, but it can be used also to describe things which are high and thin, shapewise s.a. trees, buildings, ladders, lamp posts ... i.e. things that in English are said to be 'tall', not 'high':
a tall tree; 높은/키가 큰 나무
a tall building; 높은/키가 큰 건물
a tall ladder; 높은/키가 큰 사다리
a tall lamp post, 높은/키가 큰 가로등 기둥
(2) --> DLG examples:
"저 건물이 큽니다." (That building is big) => 큽니다 is from 크다 = be big/large [size]
"학교가 높습니다." (The school [building] is tall) => 높습니다 is from 높다 = high [height], but as it is used to describe 'building', it stands for "tall".
"그 나무는 그만큼 높습니다." (That tree is that tall) => 높습니다 is from 높다 = high [height], but as it is used to describe 'tree', it stands for "tall".
"저 여자는 키가 이만큼 큽니다." (That woman is this tall.) => 키가 큽니다 is from 키가 크다 = tall [height for people]