$1$. My salary is low, however the job is hard 

        Although the job is hard, my salary is low

        In spite of hard job my salary is low

$2$. We decided to buy this house, however we didn't have enough money

       Despite not having enough money we decide to buy this house

        Although we didn't have enough money. we decide to buy this house

$3$. He didn't pass the exam, however he worked very hard 

        Despite working very hard he didn't pass the exam

        Although we worked very hard, he didn't pass the exam

1. I really like him, however he just thinks of me as a sister.

    I really like him although he just thinks of me as a sister.

    I really like him despite the fact that he just thinks of me as a sister.

2. I want to go out, however I am sick.

    I want to go out although I am sick.

    I want to go out despite being sick.

3. She came there, however she didn't want so.

    She came there although she didn't want so.

    She came there despite not wanting so.