完 wán (= complete) and 懂 dǒng (= understand) are complements of result.
In order to express that the result can be attained or is attained, the following structure is used:
verb + de + complement of result.
| 你 | 看 | 得 | 完 | 吗 | ？ |
| nǐ | kàn | dé | wán | ma | _ |
| you | look | get | complete | particle | _ |
| you | look, read | get | finish | particle | ？ |
| Can you finish reading (it)? | |||||
| 你 | 听 | 得 | 懂 | 吗 | ？ |
| nǐ | tīng | dé | dǒng | ma | _ |
| you | listen | get | understand | particle | _ |
| you | listen | get | know, understand | particle | ？ |
| Do you understand? | |||||