他tā 话huà 说shuō 得de  很hěn 慢màn 。v.s. 请qǐng 把bă 话huà 说shuō 慢màn 点diăn 儿r 。v.s. 他tā 话huà 说shuō得de  慢màn 了le 点diăn 儿r 。

He speaks slowly. v.s. please speak slower. v.s. He speaks too slowly.

说shuō 得dé 很hěn 慢màn , 说shuō 慢màn 点diăn and 说shuō 得de 慢màn 了le 点diăn do not have the same meaning, although they look 差chà 不bù 多duō (more or less the same).

他tā 话huà 说shuō 得dé 很hěn 慢màn simply states the reality that He speaks very slowly. The sentence pattern is ‘Verb 得de 很hěn adjective’.

请qǐng 把bă 话huà 说shuō 得de 慢màn 点diăn 儿r 。The sentence pattern ‘Verb 得de Adjective 一yì 点diăn 儿r’  expresses the hope/ order/ requirement that Please speak slower.

The third sentence pattern is ‘Verb 得de adjective了le  点diăn 儿r ‘ It expresses a complaint or unsatisfactory feelings; 他tā 话huà 说shuō 得de 慢màn 了le 点diăn 儿r，He speaks a bit slow (I wish he would speak a bit quicker.).

Compare the following three sentences:

我wǒ 动dòng 作zuò 一yí 向xiàng 很hěn 慢màn  。I do things slowly.

动dòng 作zuò 慢màn  点diăn 儿r ，别bié 摔shuāi 倒dăo 了le ！Slow down! Don’t trip over.

我wǒ 动dòng 作zuò 慢màn 了le 点diăn 儿ér ，东dōng 西xī 全quán 都dōu 被bèi 拿ná 光guāng 了le 。I was too slow, Everything has been taken.