There is an internship in the third semester so I'd really love to learn about xx.
There is an internship in the third term which would be a great opportunity to learn lots about xx.
どちらも「3学期にインターンシップがあるので、XXをしっかり学びたいです。」という言い方です。何のインターンシップなのかわからないので、XXのところに学ぶ内容を入れてみてください。
1) There is an internship in the third semester so I'd really love to learn about xx.
2) There is an internship in the third term which would be a great opportunity to learn lots about xx.
「3学期」は third semester や third term と言えます。
「しっかり学ぶ」は really learn about ... や learn lots about ... と言えます。
ご参考になれば幸いです!
I have an internship in the third term, so I want to learn as much as I can.
I have an internship in the third term, so I want to learn as much as I can.
『3学期にはインターンシップがあるので、しっかり(できる限り多くを)学びたいです。』
日本語の「3学期」は英語で the third term や the third semester と表現するのが一般的です。「しっかり学びたい」という前向きな気持ちは I want to learn as much as I can(できる限りしっかり学びたい)と言うと、日記にぴったりの自然な英語になります。