If I were given a bit of time, I could speak with the right grammar, but I can't do that when I have to speak spontaneously.
ご質問ありがとうございます。
"If I were given a bit of time,"=「もし私に時間が少し与えられたら、」
"I could speak with the right grammar,"=「私は、正しい文法で話せる」
"but I can't do that when I have to speak spontaneously."=「でも、その場で話さなければいけないときは、出来ない。」
ご参考までに。
I have a hard time paying attention to my grammar when I speak English.
I find it difficult to really think about my grammar when I'm conversing in English.
この場合、次のような言い方ができます。
ーI have a hard time paying attention to my grammar when I speak English.
「英語を話している時、文法に注意を払うのは難しい」
to have a hard time ~ing で「〜するのが難しい」
to pay attention to my grammar で「文法に注意を払う」
ーI find it difficult to really think about my grammar when I'm conversing in English.
「英語で会話をしている時、文法をよく考えて話すのは難しく感じる」
to converse in English で「英語で会話をする」
ご参考まで!