"Assertively in English" typically refers to expressing oneself with confidence and vigor. It involves using language that strongly conveys your intentions, opinions, or needs, often emphasizing clarity and directness.

How would one convey a strong tone using English while avoiding exclamatory elements or particles?
In conversational English, both the tone and emphasis of the voice can convey a strong, intense expression of emotions or opinions, whether it’s in those sentences or the ones that precede them.
Forming sentences in English often requires careful consideration of word choice, sentence structure, and sometimes capitalization for emphasis.

Strongly assertive in English is "forcefully declarative."