tā xiànzài dǒng le, wǒ yě dǒng le.

No. 了 after 懂 marks a change of state or new situation: “has come to understand / understands now.” It’s not simply past tense. With a stative verb like 懂, 懂了 means the state has newly begun.

Examples:

• 她懂了 = She now gets it (she didn’t before).
• Without 了: 她懂 = She understands (a general fact, not highlighting a change).

Each clause has its own predicate, so each uses 了 to mark the new state. If you drop the second 了:

• 她现在懂了，我也懂。 The second clause becomes a general statement (“I also understand (in general)”), losing the “now I get it” feel.
• If you drop both: 她现在懂，我也懂。 You’re simply stating facts, not emphasizing a recent realization.

Using 了 in both keeps the parallel “now-understands” meaning for both subjects.

也 means “also/too.” It goes after the subject and before the verb/adjective:

• Correct: 我也懂了。
• Incorrect: 也我懂了 or 我懂也了.

In the full sentence, 我也懂了 means “I also (now) understand,” linking back to the first clause.

Use 也 to say “also (in addition).” Use 都 when referring to a plural subject meaning “both/all.”

• Current pattern: 她现在懂了，我也懂了。
• With a shared plural subject: 她和我都懂了。 / 我们都懂了。

You can combine them when the scope differs:

• 我们现在也都懂了。 = Now, we also (in addition to others/other things) all understand.

Not in this meaning. 还 most often means “still/yet/also (in addition)” but with a sense of continuation or “in addition to what’s already mentioned.” 我还懂了 is usually odd here. Typical uses:

• 我还不懂。 I still don’t understand.
• 我还没懂。 I haven’t understood yet.

For “also,” stick with 也.

• 懂: understand (often of meaning/explanation); can be immediate “got it.”
• 明白: understand/be clear about; close to 懂, slightly more colloquial/explicit clarity.
• 知道: know (facts/information), not necessarily “understand the reasoning.”
• 理解: understand deeply/with reasoning or empathy; more formal/deeper.
• 了解: have a grasp/insight into, be familiar with.
• 会: can/know how to (ability), not “understand.”

In this sentence, 懂了 is “now she/I get it.” You could also say 明白了 with a similar feel; 理解了 sounds deeper.

懂 can be transitive or intransitive.

• With object: 我懂中文。, 我懂你的意思。, 我听懂了这句话。
• Without object: 我懂了。 (object is understood from context) In the given sentence, “what” they understand is implied by prior context.

• 不懂: don’t understand (general/at present).
• 没(有)懂: didn’t understand (completion not achieved at a past point or in an attempt); more natural with a verb like 听/看: 没听懂.
• 还不懂: still don’t understand (contrary to expectation).
• 还没(有)懂: have not understood yet (but expected to).
• 不懂了: no longer understand (a change to not understanding).

To ask about the change-of-state: 你懂了没有？/ 懂了没？

Yes, very common:

• 听懂 (understand by hearing): 我听懂了。
• 看懂 (by reading/seeing): 我看懂了。
• 读懂 (by reading): 我读懂了。
• 弄懂 / 搞懂 (figure out, manage to understand after effort): 我终于弄懂了。

Use 都 with a plural subject:

• 我们都懂了。 (We all/both understand now.) If you want to add “also” relative to something else, you can say:
• 现在我们也都懂了。 (Now, we also all understand.)

No. Place time expressions before the verb but after the subject, and keep 也 before the verb. Natural options:

• 我现在也懂了。
• 现在我也懂了。