One option is the word offer.
No, the word "proposal" is not an adverb.The word "proposal" is a noun.
Suggestion is another word for proposal answer: engagement?
Proposal letters are of many types, for example, business proposal letter, sponsorship or marriage proposal letter. For a better insight you can surf the web. I found a website for you, see if it is useful.
The word is spelled proposal, just as you spelled it. Propose is the root word.
Daily is a good word for a 5 letter word for everyday.
The link below has an example of business proposal letter, hope it will be helpful.
loose is a 5 letter word for not taut.
Inter is a 5-letter word for bury.
small 5 letter word
The 5 letter word for equal is 'alike'.
what 5 letter word begins with s- a living thing-second 5 letter word ending in d
A 5 letter word that starts with an L is Lipid