Your lessons are continuing to be rated highly and it will become difficult to take your class.
あなたの your
授業 lesson
評価 rate
上がりつつあり are continuing to ~ highly
予約が取りづらくなる it will become difficult to take your class
~「つつあり」は are continuing to ~ で言えます。
例文 The temperature is continuing to rise.
「気温が上がりつつあります。」
参考になれば幸いです。
オーストラリア 
日本 
