Hello sara.

Saving history will not have a considerable impact in the performance in Firefox in modern computers. But if you are experiencing performance issues because of history, see this support article.

To disable history saving, go into Tools > Options > Privacy > Firefox will: and set it either to Never remember history or Use custom settings for history (and configure it how you like).

See the Delete browsing, search and download history on Firefox KB article for information on settings in this regard.

Not saving history will not slow down your Firefox.

As described in the article, you can choose to not save any history at all, save it only in an active session, or keep it. You can also start a "Private Browsing" session if you have history enabled, but don't want Firefox to remember history for a certain session. And you can always clear the history completely if you wish to do so.

For further help with history-related topics, you could check out this search in the KB: https://support.mozilla.com/en-US/search?qs=s&q=history - or ask further questions in this or a new thread here on the forums.

Be aware that if you disable the history or use Private Browsing mode then visited links won't show as visited.