The sooner you find the (diseases/illness) the easier it is to treat; however, the longer it takes the more difficult it becomes.
The sooner you start treatment, the better the chances of recovery; however, the more you delay the more difficult recovery becomes.
「治療まで時間が早い程治癒率は上がり時間が経つと治りにくい」は英語で The sooner you find the (diseases/illness) the easier it is to treat; however, the longer it takes the more difficult it becomes もしくは The sooner you start treatment, the better the chances of recovery; however, the more you delay the more difficult recovery becomesになると思います。The sooner you start treatment, the better the chances of recovery; however, the more time passes the more difficult it is to recoverも大丈夫だと思います。
treat - 治療する
illness, disease - 病気
find - 見つける、発見する
recovery - 回復
to start treatment - 治療を始める
delay- 遅らせる、遅くする
difficult - 困難な, 難しい
time passes, time goes by - 時間が経つ
イギリス 
