She speaks haltingly because of her English accent
An adverb is a word which modifies a verb, such as: She haltingly spoke of her experience. In this sentence, the word "haltingly" is the adverb. In the sentence you provided, "How" is not an adverb.
Speaking haltingly is the bad habit which can lead to decrease our ability.
Haltingly is an adverb.
http://www.merriam-webster.com/dictionary/haltingly
Some synonyms for the word slowly include the word calmly, casually, and lazily. If you feel adventurous or want to seem particularly studious, then you may use other words such as unhurriedly or haltingly.
Can you use the word concluding in a sentence? Done.
You can use the word Truss in a sentence like this.
Just use it! Or do you mean, can you use the word beheld in a sentence.
How do you use the word decibel in a sentence?What is decibel used for?
Since that is not a word I would not attempt to use it in a sentence.
You just did use the word colonize in a sentence.
You can use the word Terrorist in a sentence as " Muslims are not terrorist ".