請教英文文法4條問題....

We may be buying a new house同
We may buy a new house.意思上有咩唔同,,,
同埋may could 後面d動詞唔係唔使轉咩?..

兩句意思係一樣，係第一句因為BE 係動詞，所以後面既BUY 要轉做ING FORM.
無錯，MAY 同COULD 後面係唔需要轉，但係第一句度，由於有BE 呢個動詞，BUY 一定要轉 ING FORM.

He avoided giving me a definite answer.<--呢句係Gerund??
He avoided to give me a definite answer.咁同呢句有咩唔同..

兩句意思都係一樣，只係用咗唔同既GRAMMER. 第一句係ING FORM第二句係用咗TO INFITY.

It is of great importance fighting against pollution.<--
這一句說是運用了gerund ...係米因為句子已經有is 呢個verb 所以要將其他verb都轉晒做gerund??

係呀.......煩

Fishing in this lake is forbidden.
To Fish in this lake is forbidden.意思一唔一樣?

意思一樣，但係GRAMMER用法有唔同，第一句係FISHING 開頭，由於FISHING 係解釣魚，係一個動作，所有英文句子如果係要動作開頭既一定要用ING FORM. 所以你睇到呢句後面係有個IS 做返動詞。\但係To Fish in this lake is forbidden....好抱歉，我好似未見過呢個句子結構........我諗你都係用返Fishing in this lake is forbidden好啲