Adjective + 得 + 不得了
When used as an adjectival complement, 不得了 intensifies the preceding adjective to mean "extremely" or "terribly." It appears after an adjective with 得 to express that something has reached an overwhelming degree. For example, 热得不得了 means "extremely hot."
今天热得不得了,我一步都不想走。
jīntiān rè de bùdéliǎo, wǒ yī bù dōu bù xiǎng zǒu.
It's unbearably hot today; I don't want to walk a single step.
孩子们高兴得不得了,一直在笑。
háizimen gāoxìng de bùdéliǎo, yīzhí zài xiào.
The children were incredibly happy and kept laughing.
期末考试难得不得了,好多人都没及格。
qīmò kǎoshì nán de bùdéliǎo, hǎoduō rén dōu méi jígé.
The final exam was incredibly difficult; many people didn't pass.