Fix joomla website (updated)

Here is the case: The owner of the old server where the website was, gave me all the files (public_html) and sql . I uploaded the files and dumped the sql. The new server's (iPage) php version (7.1.1) is later than the old server's (5.3.29). Other than that Joomla version is the same. I don't have any access to the old server or other files than the ones I already uploaded. When I visit the website in my server (iPage) I get this error: "Using $this when not in object context" . If the website is not up and running no payment will be awarded. I don't want to downgrade the php version on my server. The problem is caused by an extension, maybe is not compatible with php 7.1.1 ? Because if I disable this extension then site is working (with the booking part missing and getting this error: Error: SQLSTATE[42000]: Syntax error or access violation: 1104 The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET MAX_JOIN_SIZE=# if the SELECT is okaySorry, there is currently no availability.)