1. "Залезть на лошадь гораздо проще, чем слезть с неё" ~ "It's way easier to get on a horse than to get off it". "Тогда я понял, что должен слезть с этого лекарства" (informal) ~ "Then I realised I had to get off that medicine" 2. There's no such word in Russian, it's either "чехол" = "case" (a noun), or "чихал" = "sneezed"/"was sneezing" (a verb in the past tense, imperfective, masculine). So, if you mean the former, "Она бросила монетку в чехол от гитары" ~ "She tossed a coin into the empty guitar case" "Мне нужен чехол для моего телефона" ~ "I need a case for my phone" If you mean the latter, "Он чихал и кашлял всю неделю" ~ "He has been sneezing and coughing all week". "Чихал он на ваши жалобы" = "He couldn't care less about your complaints". (literally: "Sneezed he at your complaints"). Note it's a verb–subject–object sentence; in Russian you can sometimes use VSO order for emphasis. 3. As other people have already mentioned, the word "чресла" is not used very often. You can find it in some archaic expressions (for example, "огонь моих чресел" ~ "fire of my loins") and in some religious texts (e.g., "Посему, возлюбленные, препоясав чресла ума вашего, бодрствуя, совершенно уповайте на подаваемую вам благодать" = "Therefore having girded up the loins of your mind, being sober-minded, set your hope fully upon the grace being brought to you") but basically that's about it.

1. Чтобы остаться невридимым, ты должен слезть с крыши. 2. Я рассыпал перец и поэтому долго чихал. 3. I recommend you not to use "чресла". It's archaism

В Библии слово «чресла» встречается 33 раза. ЧРЕСЛА – Симфония для Библии: https://bible.by/symphony/word/23/339/

Слова "Чехал" в русском языке нет. Или "чихал" или "чехол". Я чихал не переставая. Я положил удочку в чехол.

I must say that the word "чресла" is not common nowadays. It's rather bookish:)