"I wasn't able to speak English as much as I can now."
- "I wasn't able to speak english compared to now."
この文は合っていますが "was not" より "wasn't" の方が自然な言い方になります。
- "I wasn't able to speak English as much as I can now."
”I am" を "I can now" 「私は今できる」に直しました。
"as much as I can now" の代わりに "as well as I can now" も使えます。
"I wasn't able to speak English as well as I can now."
I wasn't able to speak English nearly as well as I can now a long time ago.
I couldn't speak as much English as I can now when I was younger.
ーI wasn't able to speak English nearly as well as I can now a long time ago.
「昔は今ほど英語が話せなかった」
not nearly as ... as「〜より全く…でない」を使って表現できます。
a long time ago で「昔・ずっと前」
ーI couldn't speak as much English as I can now when I was younger.
「若い頃は今ほど英語が話せなかった」
I couldn't speak as much English as I can now「今ほど英語が話せなかった」のようにも表現できます。
ご参考まで！
オーストラリア 
カナダ 
