I've heard that 40% of all ramen restaurants close within one year of opening.
Someone told me that two-fifths of all ramen shops close less than a year after they open.
４割 = forty percent (40%), four-tenths (4/10), two-fifths (2/5)
〜から1年以内に = within a year of, less than a year (after〜)
もし「開店から1年以上営業を続ける」だったら「stay open/stay in business for more than a year after opening」「are still in business more than a year after they opened」になります。
「らしい」 = I've heard that, someone told me that, it is said that
証拠はないけど、それは本当みたいだったら「it seems like〜」「I feel like〜」でもいいです。