Apparently (question a bit hard to make out as presently written) you have a citrus tree with sharp thorns that produces bitter oranges.

You should be able to use that tree as a rootstock to graft less thorny and sweeter varieties of citrus to. You can attempt grafting multiple different varieties even, though maintaining such a tree can be a bit of work, as usually one variety will tend to take over, if left to itself.

Some citrus grafting questions and answers:

Can I graft a Navel or Valencia orange tree onto an established citrus tree?

Can I graft a branch of a sweet orange onto a sour orange tree to get sweet fruit?

Can I graft a citrus using two different techniques simultaneously?

Why does the lime half of a grafted tree suffer, while the lemon half thrives?

Apparently (question a bit hard to make out as presently written) you have a citrus tree with sharp thorns that produces bitter oranges.

You should be able to use that tree as a rootstock to graft less thorny and sweeter varieties of citrus to. You can attempt grafting multiple different varieties even, though maintaining such a tree can be a bit of work, as usually one variety will tend to take over, if left to itself.

Some citrus grafting questions and answers:

Can I graft a Navel or Valencia orange tree onto an established citrus tree?

Can I graft a branch of a sweet orange onto a sour orange tree to get sweet fruit?

Can I graft a citrus using two different techniques simultaneously?

Why does the lime half of a grafted tree suffer, while the lemon half thrives?

Can a lemon tree become an orange tree?