I can't express my thoughts in English as well as I would like to, but there are many things that are going through my mind.
ご質問ありがとうございます。
"I can't express my thoughts in English as well as I would like to,"=「英語では自分の考えを思うように表現できない。」
"but there are many things that are going through my mind."=「でも、沢山のことが頭の中にあるのです。」
ご参考になると幸いです。